SuzukiHayabusa.org
TECHNICAL => ALL MOTOR TALK => Topic started by: Stocker64 on March 20, 2008, 08:11:50 AM
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If any of you were trying to build a big 1397 what combo would you use,comp,cams ect. :?:
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Street or drag only?
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drag only spaz,I have one that makes 210 with mrx01.I want more!
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(http://img.photobucket.com/albums/v485/Johnnycheese/carson.jpg?t=1205460851)
93 pump gas STOCK head and Yosh cams
tiforce pipe
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that would be very close to the output of a gen2 tuned with a pipe.We have one in australia running 9.43@150mph and 120mph half track just lowered with a pipe untuned and airshifted.Stock length and 737lb total weight.
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If any of you were trying to build a big 1397 what combo would you use,comp,cams ect. :?:
just went through the same process ... As building one.
First ordered wisecos, sent block for rebore and nikasil and was about to get yoshi cams.... But then start to talk with Brock. He explained how there is differences in pistons, how nikasil process is different in some places, how cams may require certain amount of additional spacers if targetting to run an extended ecu. Additionally he talked about the starter pin strengt in big bore high compression engines and gear pins requirements for higher power engines. Now I have two sets of parts to build a couple of engines ...
This reminded me about two key points:
1) The parts used should be a tested combination where the things like squish is known for intended piston/cam/rods/rpm target combo.
2) A highly experienced builder (and a good salesperson) can explain what is needed for a certain power target. Its a sum of details which works well together.
Therefore what ever is chosen, best way is to talk direcly with an experienced builder who can instruct in the parts selection process with in detail answers and installation instructions. In my case that was Brock (www.brockracing.com) because of knowledge and the very good installation instructions that is avail from their internet pages.
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:thumb:
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My motor is a relitively mid combo consisting of a custom set of je,s with a modifyed compression height,a stock length carrilos,"small in racing terms" a web 378 intake cam with a stock intake on the exaust side,they are degreed at 106,108.I hand ported the head myself concentrating on velocity,instead of volume.I started by leaving the runner in front of the intake guide,and raiseing the roof slightly trying to create a slight turn into the bowl area,in where i worked the short turn radius and increased the bowl area silghtly.My theary was to speed up the air on either side of the guide in hope to increase velocity.I have seen on many of heads where the guide boss was removed completly up flush with the roof.I am not a head porter by no means,but i have seen alot of aftermarket automotive racing heads ported,and have flowed alot of heads myself.I think that velocity,not volume will make better power through the powerband,especially at mid lift since the valve will travel through mid lift twice,once on the way to peak lift and once to closeing.On the exaust side i did remove the runner and raise the roof slightly trying to create a smooth radius ot of the cylinder head,in theory that if i filled the cylinder with more volume by velocity,i would need a larger port to evacuate to cylinder.I know that there are alot of varibles that contribute to volumitric effencity.My bike is a full weight busa sitting at 64"On my first pass i left with a 1.51 60ft.went 123 in the 8th and 152 out the back,spinning from the 8th out.My datalogger also showed me a interisting thing,small spikes in rpm showing me that my clutch was also slipping!My goal is to put bigger cams with more duration and lift and see how fast a stock stroke motor can go wtih my knowledge.I want to raise the rev limiter and spin it up.I am reaseraching on how to do that now.I AM A RACER THAT WANTS TO GO FAST.I am not a engine builder.so any help towards my goals will be appreciated!
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Stocker64,
If I were you, I'd contact Bob Carpenter. My buddy just got his Busa back from Bob; it's a 1397 with the 'bigger' cams and made 238 / 128 on Bob's dyno. Bob is a very honest guy. That 1397 package was advertised at $4800, but he only charged my buddy $4400, and told my buddy it was because he figured out a more efficient way to do it.
In 23 years of fooling with dragbikes, I have to say that is the 1st time I have EVER heard of a builder charging a little less than advertised ...... he could have kept the extra $400.
www.carpenterracing.com
Good luck & Happy Easter.
Mike
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My buddy just got his Busa back from Bob; it's a 1397 with the 'bigger' cams and made 238 / 128 on Bob's dyno.
Wow, thats big numbers for a 1397... Has it been dynoed on another dyno to qualify those numbers?
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My buddy just got his Busa back from Bob; it's a 1397 with the 'bigger' cams and made 238 / 128 on Bob's dyno.
Wow, thats big numbers for a 1397... Has it been dynoed on another dyno to qualify those numbers?
That would be my bike Mike mentioned. It made 236 not 238 and 128 ft lbs.. It is a stock WB(short chain) Ti Force pipe. It is with oxygenated fuel as well. Don't know how accurate the number is but our other friend just dynoed his bike built by himself another 1397 at a different shop recently and it made 218 on pump gas. So if you take his bike and add oxygenated fuel and take my bike and run pump gas they would probably be within 6-8 hp of each other at most. I believe that my bike has a little bigger cam than his does also. The bike now has an arm +3 and is still in pieces but will be back together in a week or so. I have no clue how fast the bike will run but I have only heard good things about Bob and he was excellent to me and spent quite a bit of time talking and explaining things at his shop which is extremely hard to do with a shop that had at least 25 bikes being worked on. I think everyone knows dyno numbers differentiate from dyno to dyno, and I built this bike to race so that's what matters to me.
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:thumb: let it rip!
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That would be my bike Mike mentioned. It made 236 not 238 and 128 ft lbs.. It is a stock WB(short chain) Ti Force pipe. It is with oxygenated fuel as well. Don't know how accurate the number is but our other friend just dynoed his bike built by himself another 1397 at a different shop recently and it made 218 on pump gas. So if you take his bike and add oxygenated fuel and take my bike and run pump gas they would probably be within 6-8 hp of each other at most. I believe that my bike has a little bigger cam than his does also. The bike now has an arm +3 and is still in pieces but will be back together in a week or so. I have no clue how fast the bike will run but I have only heard good things about Bob and he was excellent to me and spent a quite a bit of time talking and explaining things at his shop which is extremely hard to do with a shop that had at least 25 bikes being worked on. I think everyone knows dyno numbers differentiate from dyno to dyno, and I built this bike to race so that's what matters to me.
Good post .
Bob's engines can move on out ------- enjoy your racing season :thumb:
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I can't wait for a little better weather and to get the bike running. I took a few years off from racing as I bought a house and didn't have as much spending money, but I still have a 92 1100 that is 64"WB that has been 8.81 @ 155 on motor, built by Rick Stetson/Rick Smith. I also had a 96 1100 stroker that Coby Adams built as well that went 9.20 @ 152 @ 60". I had to get my license renewed again last year as it was a year expired and that was my first time in a few years, but I always had the bug in me. Funny thing us dragracers always end up back where we started. :thumb:
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Lee you're still my DOGG, man ..... sorry if I gave out too much info ..... Bob did you right, so I like to spread good news ..... see you soon.
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Lee you're still my DOGG, man ..... sorry if I gave out too much info ..... Bob did you right, so I like to spread good news ..... see you soon.
Mike, I would have told anyone that asked about my experience with Bob Carpenter. The thing about him is he is not arrogant or big headed at all. He is as down to earth as anyone you'll ever meet.
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Graph?
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(http://i29.photobucket.com/albums/c270/whtrthanu/dyno1397.jpg)
Heres one i just finished, it has .385 intake, and this is on pump gas, so if we run mrxo1 I bet it would be over 230......The air has to be real good, but it can be done, with the right head on it...
And i have my 92 oil cooled it runs 161mph on motor @ 60".....its been 8.80s
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has anyone used web 415/395 or 445/415 on a high compression 1397,say compression was around 15 to 1? what ones would you use?
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(http://i29.photobucket.com/albums/c270/whtrthanu/dyno1397.jpg)
Heres one i just finished, it has .385 intake, and this is on pump gas, so if we run mrxo1 I bet it would be over 230......The air has to be real good, but it can be done, with the right head on it...
And i have my 92 oil cooled it runs 161mph on motor @ 60".....its been 8.80s
thats some good numbers on pump gas.
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has anyone used web 415/395 or 445/415 on a high compression 1397,say compression was around 15 to 1? what ones would you use?
wouldn't your builder know this???
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Gotta love the differences in the dyno numbers.... :lol:
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jonny,I am my own builder?I am asking general questions about combs that may work for a high winding 1397 without spending a bunch of money!I have no problem in picking camshafts for my 600ci svo block c-460 headded race motor or my 520ci bluethunder/raised port cylinder head street class motors! I know that you know about strong motor combo's with bike motors,so instead of asking about engine builders,how about shareing some info?how do those cam combo's work?you must know,you are a engine builder!so how about some data?
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I see that 230 hp chart is "actual" hp. Whats the corrected Hp on that pull?
You have to compare apples to apples. Corrected hp vs actual hp is like comparing a busa to a zx14.
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Like i said Jim, it has to be in good air to make the big numbers, the corrected numbers for this motor were 217hp...that was for this graph, still not bad for a 1397. Dont forget it had a sidewinder, but it also was 66 inches long. The cams were laid back alittle bit more than i usually set them at. It also had an oring chain on it, the pipe had the packing in it still, Its in the head, I am trying something different, and it seems to be working, my .250-.300 lift flow numbers were improved alot, while the peak air flow didnt change at all. tHe head only flowed 255 @.450 in 28". Thats nothing really different compared to whats out there.
The motors that i finished with 2 intake cams will make around 195 or so corrected on pump gas, and around 200 or so actual. With fuel in them and really killer air you can bet they would make 210-215hp. Some days over here are crazy air days. c/f is around .92. You know that bob down by the water has the same air as us, so thats why he gets them big hp numbers........On a big motor you can see 15hp from good air............ :thumb:
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You know that bob down by the water has the same air as us, so thats why he gets them big hp numbers........On a big motor you can see 15hp from good air............ :thumb:
Are you referring to ramming air into the airbox?
Or are you seeing big bhp fluctuations based on weather conditions?
Reason i ask is the only times i've ever seen that kind of jump is when the dynojet weather station goes south (of which i have one fail per year on average so far). When its running tight and accurate then the corrections in SAE don't vary much all year round.
Just curious here, not trying to start another weather station debate.
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"E" i am refering to weather conditions. There isnt a problem with my stack, I have check my sae numbers with other dynos in the area several times. AS far as actual hp we live at sea level so the barometer has been as high as 30.8 several times and the humidity as low as 10%. Now these are mine shaft conditions, but none the less they are real.Bobs shop is near Atco, thay are below sea level i believe. This is why the track is know for being very fast. With my dyno, it actually reads a few hp lower on SAE than the other dyno i compared it too, Example, a stock busa, early year, makes anywhere from 148hp to 153 sae on mine. I compare my runs to my buddies dyno in another state and we are within 1 hp of each other on builds or stock bikes comparisons.....anothjer example is a 02 GSXR 1000 i just did, 3mm pistons cams and brock pipe, 1mm over intakes, on pump gas it made so far 176hp sae, i put mrxo1 and in real good air the other day it made 192hp!!! Even SAE with fuel it still made 182 hp, so the air was so good it was giving 10 hp.....
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has anyone used web 415/395 or 445/415 on a high compression 1397,say compression was around 15 to 1? what ones would you use?
My engine builder used 415/395's in my 1397 and they worked great. The added displacement of the 1397 makes up for the loss of low end you would normally get from the big cams, but the gain in high end is quite dramatic all the way to redline. The 445/415's might be overkill, imo, for a 1397.
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I used that setup before. 427/410 cams, high comp domes at 15.5.1 comp. It ran like a 1507. you won't be disappointed. 8.40's at 164 fully dressed at 65 inches. Stock bodywork and wheels, Lockup clutch.
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I had a 1397 that I built w/ Wiseco's from APE, WEB .395I/.378E cams, mild ported head(by me), small box mod with short stacks. It made 208 hp/120 tq on 93. Considering I did all the work, I was happy with it. Some of these other guys are getting stupid numbers out of theirs. Stupid as in GOOD! :lol: I Just don't have their skills.
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Most Ive ever seen out of a 1397 (REAL NUMBERS ANYWAYS) was 236 on nutec fuel . That was an Eric Canada built motor several years ago . havent seen one pull that since . Even eric was floored :lol:
That was on the same dyno we allways use so it wasnt a happy dyno factor . Erics good !
The motor didnt live a long time but the bike had big electrical issues and the electronics didnt work right so im sure that was a factor in its ultimate demise .
That nutec was some nasty stuff too...
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I have seen 235hp out of a dome piston 1397cc
and 229hp out of flat tops @ .039" piston to head. I run my about .041"-.042" with stock rods.
I know Eric likes to run his tight.
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just got it off the dyno with 415/395 flat top je,s hand ported by me with cooper valve job with mrx01 205hp110tq,I think it may still have more in the tune,it has small air box mod with stock stacks?I am now going to change stacks and mess around wit intake track lenghts and put back on dyno.
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Just to understand what you guys are referring to, are you talking dynojet rwhp or real crank hp like factorypro real rwhp ? I am locally here seeing a big difference between dynos. Rwhp by dj250 djhp is almost the same as real calibrated crank hp ???
http://www.factorypro.com/dyno/true1.html (http://www.factorypro.com/dyno/true1.html)
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petrik,mine was measured on dynojet250i,been haveing small problems with combo,I had to get injectors cleaned that put me down for a day!I had to put a standalone fuel system also,going to spray 100 progressively as soon as i get it sorted out.I have been having problems with editor so i cannot try some different high rpm things :lol:I will put it back on dyno next week and try them then :thumb:
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Here are my views that may or may not help towards the ongoing dynojet and varying horsepower question:-
Yamaha claims for crank horsepower.
2006 R6 - 133bhp. My 250i - 106bhp
2004 R1 - 172bhp. My 250i - 152bhp
Stock busa is around 152-155 on my machine, not 175+ as suzuki claim.
I've checked airbox pressure readings on the dyno versus track data and it doesn't account for the percentage increase some of these manufacturers claim.
I know 2 main brands of dyno that read much higher than dynojet.
250i is measuring rear wheel horsepower and what some of these articles claim is not true of a current dynojet 250i.
My machine is regularly compared with dynojet uk's machine at the BSB meetings. That matches to within 1bhp and that also matches to within 1bhp of all 3 of their dynos. So at worst you could see a 2bhp difference but that can be accounted for in changing weather and/or heat in the dyno process. But compare it to the dynojet machine on the Arrow truck at WSB meetings and they have, how shall we say, a slightly optimistic view on the numbers ......
There are a few shops i have compared against who run their machines with pressurised rooms and faulty weather stations who are regularly way way over our numbers. One recently got rumbled by one of the biggest magazines here where they found a 21bhp on a k7 1000. There are also those shops who mess with tyre pressures, strap tension, changing rear tire and also have scant regard for tire slip. Poor understanding and crooked methods are often the reason for such a varying range of numbers. Numbers sell, so many people take advantage of this.
Just curious. But who says that factory pro is rear wheel horsepower? Not saying they are wrong but if i stand here and tell you this is a real Van Gogh painting, would you believe me just because i say it is and then hand over your money? Hey maybe dynojet are wrong. I didn't design either. But i do know a 250i can be very consistent with another 250i if used and maintained by a keen operator.
Just my 2 cents on the ongoing dyno debate.
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Stock busa is around 152-155 on my machine, not 175+ as suzuki claim.
So that old stock busa 152-155 is crank hp? I have seen a figure of about 158hp @ crank with a recently calibrated Dynostar dyno.
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No, rear wheel according to dynojet. Its a bit more than you said your different brand of machine shows but less than an engine dyno. I know someone who has a superflow 902 engine dyno and he reads more with that than his old dynoket 150 which was higher than the new 250's read. I have also seen variation between several different brands of so-called "real bhp" dynos. So i guess we are all wrong maybe????
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Suzuki typically uses Brake / net / crankshaft horsepower (power delivered directly to and measured at the engine's crankshaft) .......which is what the 175HP is. In the States a stock Busa usually comes in around in the low 150's RWHP on pump and using SAE. For all of the obvious reasons, builders are now advertising power using STD reference while using an oxygenated fuel which adds an easy 10 HP or so over the same engine being tested on pump gas using SAE reference conditions. So the magic 220 is more like 210 on pump gas using SAE.
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Stock busa is around 152-155 on my machine, not 175+ as suzuki claim.
That is exactly what I have always seen for stock,first gen busa's
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Hey Mike, just reading your signature. Cosworth made pistons for the virgin yamaha superbike team last year, i'm pretty sure. I mapped a bike for one of the engine designers at cosworth a few weeks back so if you really want some i can maybe put you in contact with him. He said they may be open to further production. Failing that i could put you onto someone else who has built me F1 quality bike stuff before.
PS. I'm not trying to trade here, just in case the mods are wondering. Merely trying to help out and make nothing out of it myself.
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Suzuki typically uses Brake / net / crankshaft horsepower (power delivered directly to and measured at the engine's crankshaft) .......which is what the 175HP is. In the States a stock Busa usually comes in around in the low 150's RWHP on pump and using SAE. For all of the obvious reasons, builders are now advertising power using STD reference while using an oxygenated fuel which adds an easy 10 HP or so over the same engine being tested on pump gas using SAE reference conditions. So the magic 220 is more like 210 on pump gas using SAE.
OK - that starts to paint the picture about the numbers advertised.
On the current dyno we use the stock busas are only 160hp @ crank, zzr1400 around 170 and K8 busas around 180@crank. I am starting to think that there still is a calibration issue between few manufacturers, in US factorypro vs dynojet and in europe Dynostar vs dynojet. The various dyno standards like DIN/SAE/STD explains other differences, but not this one...
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On a Dynojet a stock Busa makes, say, 152 while FactoryPro says "real" RWHP is 135 or so. Assuming Suzuki knows how to measure power, implied driveline losses under the Dynojet regime would be 13.1% while under FactoryPro it would be 22.8%. I think Dynojet is closer.
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On a Dynojet a stock Busa makes, say, 152 while FactoryPro says "real" RWHP is 135 or so. Assuming Suzuki knows how to measure power, implied driveline losses under the Dynojet regime would be 13.1% while under FactoryPro it would be 22.8%. I think Dynojet is closer.
Your guess is as good as mine - can we find facts ?
One way to confirm horsepower is trap speed on quarter mile if weight is known. Any statistics avail of the topic ?
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Or, top speed at WOT.
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Or, top speed at WOT.
About 160 RWHP to go 189 MPH.........153 HP plus a dash of ram air.
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On the current dyno we use the stock busas are only 160hp @ crank, zzr1400 around 170 and K8 busas around 180@crank.
How are you measuring crank hp on a busa? There is the obvious problem of a gearbox being permanently attached. Just wondering how you got around this.
I'm quite excited, been asking for some real crank dyno data for ages on this motor but nobody seems to have any. What is the actual VE?
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How are you measuring crank hp on a busa? There is the obvious problem of a gearbox being permanently attached. Just wondering how you got around this.
I'm quite excited, been asking for some real crank dyno data for ages on this motor but nobody seems to have any. What is the actual VE?
Unfortunately you are right - what I call @crank is rather negative losses added to rwhp and gearbox losses can not be fully added. Usually its only losses up to clutch. So for std engine we get 160hp and suzuki advertises 172hp meaning that 12hp is still lost inside transmission - hard to believe? Often the losses measured are in average about 9%, but an average can not be used as the losses are non linear.
With TOP speed I see the effect of air density becoming an issue. Quarter mile trap speed is a bit lower and hence better indication of the power if weight is known and we use only alike engines to compare with.
Anyway I am still puzzled why Dynostar and Factorypro have a completely different set of figures when measuring power than Dynojet ?
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Ah ok, its estimated then. I have measured coast down losses but even then i don't think its accurate enough. You can show the same coast down loss but have a rear tyre you know reads 15bhp less than the next one. Doesn't show up on losses how it saps power on acceleration - at least not on my dyno it doesn't!
No idea on the figures. Obviously factory pro is well down on dynojet and in my experience, dynostar is well up on dynojet. Very strange. Somebody must have their calcs wrong somewhere. I do know a shop who measured output power on an engine dyno for a 2007 R1. The figures they got from gearbox sprocket do not tie in with manufacturers claims minus accepted transmission loss %'s. So the question is still, does anyone really know who is right or wrong?
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Air density is not an issue as it is fundamental to drag and part of the calculation.
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Ah ok, its estimated then. I have measured coast down losses but even then i don't think its accurate enough.
Yes - what alternatives to coastin losses we have ???
I think I will go through the dyno calibration process just to understand why so much lower figures on this dyno than local dj250's. I believe that the dyno manufacturers would know the answes - maybe someone should ask from dynojet and from factorypro why so big differences ... ?
Air density is not an issue as it is fundamental to drag and part of the calculation.
Rather meant that its info very seldom logged to give comparable figures. Quarter mile trap speed is something for which a lot of data is avail on time slips ...
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I've asked factory pro and dynojet and they both say the other is an idiot and completely wrong. :(
The latest race tyres are a complete pain in the ass. The don't show huge drag on coast down as they do on hard acceleration. Rate of sweep shows differences also. Even on a 600 you can see 6bhp between a bunch of them. Doesn't matter what brand of dyno. A dunlop 16.5" slick on a superbike 2 years ago was guaranteed 15+bhp down on a touring tyre. Latest ntec slicks are about 5-8bhp down depending on compound.
Any of you drag race guys spotted bhp losses with race versus road rubber on dyno? Or do you all use road rubber at low pressure? I'm dumb to the world of drag racing if that sounds like a squid question.
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I've asked factory pro and dynojet and they both say the other is an idiot and completely wrong. :(
Or do you all use road rubber at low pressure?
That answer from both parties as it really explains everything ... I really would like to hear what is the truth as calculating HP is very easy if we look at basic physics. The dyno calibration is also based on laws of physics so the differences are coming from different formulas inside the dyno software.
On this particular dyno always 1.5bar (25psi ?) pressure for road rubber is used. Prevents slippage and gives more consistent coastdown (learned a new English word today ;-)
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I've asked factory pro and dynojet and they both say the other is an idiot and completely wrong. :(
The latest race tyres are a complete pain in the ass. The don't show huge drag on coast down as they do on hard acceleration. Rate of sweep shows differences also. Even on a 600 you can see 6bhp between a bunch of them. Doesn't matter what brand of dyno. A dunlop 16.5" slick on a superbike 2 years ago was guaranteed 15+bhp down on a touring tyre. Latest ntec slicks are about 5-8bhp down depending on compound.
Any of you drag race guys spotted bhp losses with race versus road rubber on dyno? Or do you all use road rubber at low pressure? I'm dumb to the world of drag racing if that sounds like a squid question.
Holy crap that's a lot of loss for tire. I could see if you had a car tire on the bike but???
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Its a total pain in the ass Mike. I build a race motor for someone and they bring the bike in for dyno with a bad reading tyre. They think they've been screwed over. Its a major problem with the modern race tyre.
I tested a pirelli super corsa tyre against a dunlop qualifier last year on suzuki 750. Within 10 mins then back again to confirm. Both popular road tyre. 11bhp difference. Everyone i know who takes the time to notice these things has the same issues, its not a one dyno problem. I've got a chart from dynojet showing 16bhp loss on a cbr1000rr within 10 mins also.
Its the same on a busa too so you guys better beware!!
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the race compound tires showing a big loss on the dyno is pretty well known, especially the shinkos
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Its a total pain in the ass Mike. I build a race motor for someone and they bring the bike in for dyno with a bad reading tyre. They think they've been screwed over. Its a major problem with the modern race tyre.
I tested a pirelli super corsa tyre against a dunlop qualifier last year on suzuki 750. Within 10 mins then back again to confirm. Both popular road tyre. 11bhp difference. Everyone i know who takes the time to notice these things has the same issues, its not a one dyno problem. I've got a chart from dynojet showing 16bhp loss on a cbr1000rr within 10 mins also.
Its the same on a busa too so you guys better beware!!
ET, are there weight differences between the compounds/tires?
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Its a total pain in the ass Mike. I build a race motor for someone and they bring the bike in for dyno with a bad reading tyre. They think they've been screwed over. Its a major problem with the modern race tyre.
I tested a pirelli super corsa tyre against a dunlop qualifier last year on suzuki 750. Within 10 mins then back again to confirm. Both popular road tyre. 11bhp difference. Everyone i know who takes the time to notice these things has the same issues, its not a one dyno problem. I've got a chart from dynojet showing 16bhp loss on a cbr1000rr within 10 mins also.
Its the same on a busa too so you guys better beware!!
ET, are there weight differences between the compounds/tires?
If anything race tires are lighter than street. My experience. May be different now.
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In our car we ran 143 rwhp....you can imagine I was pissed considering we had a cold cam on the hot side, PC, yosh header......
The same motor, same day in the bike made 166 (zero map) with nothing else done except it was spinning 1 tire and 2 bearing and not 2 tires 4 bearings and 2 CVs.
That is a difference of 23 hp loss, true our axles were not dead in line causing loss in the CVs….but damn…. 143 from 166!
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ET, are there weight differences between the compounds/tires?
Yes but its not just a weight issue. If i tested loaded instead of inertia it levels it out much more but there is still a rubber issue. Its like some of the rubber sucks down hard and some doesn't.
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ET, are there weight differences between the compounds/tires?
Yes but its not just a weight issue. If i tested loaded instead of inertia it levels it out much more but there is still a rubber issue. Its like some of the rubber sucks down hard and some doesn't.
Do you measure the tyre slippage by comparing wheel RPM to Tach signal RPM ?
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Yes. Winpep has a gear ratio option. The is comparing the 2 rpms. You can see slippage easily with this. Can also check coastdown easily
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Just to throw my two cents in,what about when the dyno drum wheel has some or all of the rubber nurling gone on it.Would that affect the reading?
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the only way that could change readings would be of the drum lost weight...The readings would be lower than normal........
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wouldnt the tire slip with some or all of the rubber nurling gone on the dyno drum
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it might slip, but the dyno reads engine rpm and tire speed at the same time......he graph will show a break in it usually if the tire slips......
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wouldnt the tire slip with some or all of the rubber nurling gone on the dyno drum
When the knurling gets really worn you end up pulling the straps down a bit tighter.
There is always some slip, its just about keeping it to a minimum.
For those of you who are not too familiar with slip on the dyno, this may help you to understand.
Here is a good example.
This is a k6 1000. Look at the dates and times at the top. It is 6 successive roll-ons on a cold tire.
The left hand graph is you normal power graph and the right hand one is the tire slip graph.
But if you change to a low reading tyre the slip graph does not change. It really is not a measurable thing how much the rubber sticks to the roller.
(http://www.racedevelopments.co.uk/images/k61000slip.gif)
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tuna,it seems to me is that you get less slippage with a warm tire on the dynoe drum,if Iam reading the grapf correctly.
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the only way that could change readings would be of the drum lost weight...The readings would be lower than normal........
?????????