Small Port 1397.....Dyno Graph

[Steve S]

To segue from a related discussion, I thought I would post a dyno chart from yesterdays's dyno session on a NA 1397 with Bryan and Sonny. The purpose of the session was to reconcile some data and investigate certain exhaust elements. Purely as a matter of interest, though, I should mention the engine features smallish ports, smallish cams and flat top pistons. It can very easily be ridden on the street and, when cold, readily starts on one battery; it is not, however, designed to be a daily rider on which loads of miles are accumlulated. "Old" MRX01 was used and we could have picked up a couple of more HP with fresh fuel and tuning.

[gazza414]

That's a strong 1397 

[enginetuna]

Here is one i did 2 years ago.  Stock bore, 5mm stroker, stock rods, mild cams.
One is a normal head job, the other has real small ports.
I'll leave you all to guess which one has the small ports
These runs were only a few days apart and everything was identical apart from the inlet ports.

[DarkFalcon]

  Neat stuff.

[gnd111]

So how could something so "mild" and low C/R to start with 1 battery (and only be driven when cold) not be a reliable daily driver???

Can someone please explain because things are really not making conventional sense in any of this 229rwhp "mild" 1397 that found 18 MORE rwhp just due to DA (which further clarifies all i have been argueing with Pat D about for years)...

[BusaSnoop]

What cam specs to get that kind of h.p. I still have stock cams and have no solid info on what to exspecked from a good set of cams.

[whtrthanu]

the torque on the 1397 is high, look at the similarities between the 5mm stroker and the 1397........hmmmmmm
I think the 1401 is more realistic in power, makes great torque but not a ton of peak power, great street motor

[enginetuna]

My motor was used for autograss racing.  Autograss = spaceframe car on mud oval circuit and weighs under 900lbs.  Tyres spinning most of the time, instant throttle response important, ability to recover from low rpm very important, peak power not very much.  It won national championship.  And if it sounds like a monkey sport, the top guys are spend $50,000 a year.
In answer to an earlier question on the other thread about engines for different types of application and power, you can quite clearly see how easy it is to move your power around.
Changing the exhaust port and the cams for a drag racing application easiy adds 20bhp to the peak figures.
Also adjusting the inlet filling can move power around.  I've had a lot more peak and only slightly more mid on dyno with epoxy in there versus a non-epoxy job.
There is no golden rule on when you can stop using filler.  My 1500+ busa motors have epoxy inlet and welded exhaust.  But remember, like i said before, its not always about reducing size, it can also be about changing the shape of the port   And not every port wants filler or welding rods in it.

[DarkFalcon]

ET, can you give us some idea as to the size of the small (blue) ports versus the larger (red) ports. Something like the smallest CSA? I would love to know the port speed in the 9000 to 9500 range........which is where it is starting to lose steam.

[gnd111]

the torque on the 1397 is high, look at the similarities between the 5mm stroker and the 1397........hmmmmmm
I think the 1401 is more realistic in power, makes great torque but not a ton of peak power, great street motor

Wouldn't it be a 1408?  Isn't a 5mm stroke 110cc...?

[enginetuna]

ET, can you give us some idea as to the size of the small (blue) ports versus the larger (red) ports. Something like the smallest CSA? I would love to know the port speed in the 9000 to 9500 range........which is where it is starting to lose steam.

From memory it was about 75%, maybe a touch more.

[gazza414]

I'm surprised no one has commented on the A/F numbers here?

[enginetuna]

Very lean and also the correction is +4% due to extremely low air pressure.  But then it may have been dyno'd at altitude.

I can show you graphs of bike engines where i've dropped the inlet port volume say 25% and port height at choke quite some way and the whole curve is up, more so at peak than midrange.  This busa graph is one of the few where it knocked out the top so don't take it as given that epoxy work knocks out your peak because i've done busa where the peak has gone up as well.  The other reason this peak could be down is the intake stacks and cam timing were as before and not optimised for this head.  Many variables to consider, there are very few rules.

[Steve S]

So how could something so "mild" and low C/R to start with 1 battery (and only be driven when cold) not be a reliable daily driver???

Can someone please explain because things are really not making conventional sense in any of this 229rwhp "mild" 1397 that found 18 MORE rwhp just due to DA (which further clarifies all i have been argueing with Pat D about for years)...

Mild is your description.......not mine. Big cams, domed pistons and large ports do not in and of themselves  ensure high performance and more often than not hurt efforts to build power.

Brock's flat-top pistons are perfectly fine and provide better flame travel than most domed pistons. Our cams and ports are sized for the application and we gain compression through surfacing the head, carefully managing squish and closing the intake valve early through smaller centers. The parts function very well together and sometimes we "lean-on" established assembly guidelines.

The StgII 1397, which requires aftermarket rods, typically cranks out 6 more HP than our StgI kit which usually produces 217HP to 222HP. Because of various assembly clearances, it should not be used as a daily driver on which loads of miles will be piled on the engine; it's simply not designed for this. The engine does not overheat but because of the increased "dynamic" CR and snug piston-towall clearance it can be difficult to start when hot.

[Steve S]

I'm surprised no one has commented on the A/F numbers here?

As I said earlier it was not a tuning session.........we were trying to reconcile some data as part of another test. No tuning was required to identify an exhaust element....not shown.... which has been incorporated in and depressing earlier test data. It would have been easy to add gas and go over 230 but it was not important to take those bragging rights home. Like ET said, he has seen peak numbers of around 230 on his 5mm stroker and so have we on 1397's. This particular head incorporates small ports and is designed for 10800 RPM..........the extended ECU is now taking it up to 11,270 RPM and the ports are being challenged.

[whtrthanu]

Steve, what is you intake/exhaust flow % on this motor........Is this a stock valve or larger.

[BRYAN]

This is a stock valve motor. I am not sure of the IN/EX flow %. Jason Barnett or Steve might know this.

[Johnnnycheese]

correction factor is off

[BRYAN]

correction factor is off

Johnny could you please explain.

Thanks Bryan

[gnd111]

Probably due to the low humidity and low ambient temp it should be lower than 1.04 but i am just guessing.

[Johnnnycheese]

correction factor is off

Johnny could you please explain.

Thanks Bryan

take the altitdue, the humidity , the temp and the pressuure reading anf the std comes out at about 1.02 not 1.04
229 would = about 224

[DarkFalcon]

How can STD be 1.020 when SAE is 1.014?

[Johnnnycheese]

How can STD be 1.020 when SAE is 1.014?

where did you get 1.014?

[DarkFalcon]

It came from:

http://wahiduddin.net/calc/calc_hp_abs.htm


74; 29.23; 50.

[Johnnnycheese]

what air prerssure did you use absolute or barametic?