87 930 engine rebuild dyno results!

[porschett]

I finally got a chance to dyno my 1987 930.

Results:

Horsepower: 475 HP* (dynoed at 403 HP at the wheels)
Torque: 458 ft-lbs* (dynoed at 390 ft-lbs at the wheels)
Car weight: 2750 lbs (with 1/2 tank of gas)

* w/ 15% drivetrain loss

Mods:
36mm port
K27
1 bar spring
IA fuel head
C2 cams
C2 bypass assembly
Baileys diverter valve
Borla exhaust
goingsuperfast.com headers and full bay IC
Custom powerflow intake
ARP head studs & rod bolts
Nology wires
NGK BP8ES


As you can see, my AFR is not really optimal, but I'm playing around with the WUR to slow the fuel dump when boost hits and at the same time, slow the leaning at high RPM.

Rebuild photos: http://photos.yahoo.com/nsxtc

Updated Dyno Run with new and improved AFR curve. See 2nd page.

[David]

Very nice for a CIS engine! Any plans for EFI?

[dean]

If I read that A/F correctly you will blow you motor up soon. That looks like it is close to 13 to1

[porschett]

Well, the strange thing is I spent a lot of time with the LM-1 tunning it to low 12s at 6000 RPM (actually got it to 12.1). Only then did I take it to the dyno. Now the dyno shows high 12s.

I heard that the LM-1 reads rich? Anyone heard otherwise?

My boost enrichment pressure is set at 2.1 bar. I guess I'll try to bring it down to 2.0 bar and see where the AFR stands.

[dean]

Well I would trust the LM-1. I think they are fairly accurate as long as there is no exhaust leak.

[jeff91C2T]

Thanks for posting the results!

Just curious...how did the LM1 compare while on the dyno? I've got the LC-1 and plan on doing some comparisons myself.

Your afr looks very familiar. Too rich mid range and leaning out up high. I did the WUR mod and got the same result. Just wondering how you were going to tweak the WUR? I played a little with mine (streched the spring) to push out the full enrichment. What I found is it doesn't (or can't) make much of a difference. The boost goes from nothing to full pressure in such a short rpm range that it didn't matter (much).

[porschett]

Stretching the spring won't do it. You'll have to use a stiffer spring or shim it. I'm getting mine machined so I can adjust the spring pressure with set screws. What this does is make the slope more gradual.

See photo below... The red curve is my WUR and the blue curve is the modified WUR. See how much gradual it drops the AFR and also how much of a delay when it starts to lean. This is more preferable. Brian Leask (bleask@cox.net) is going to machine mine just for this purpose.




Dummy me, I didn't have the LM1 on or even recording for that matter. I'm going to do a full run on the street while recording to 6000 RPM to see how the AFR compares.

[porschett]

Originally posted by 125shifter
Very nice for a CIS engine! Any plans for EFI?

No EFI in the future. Wish I had the funds. 8( Good luck with your EFI conversion.

[jevvy]

decent results - hey if you tilt back the feinter lines on your dyno chart they almost look like the profile of a 911 - very clever!

[WydRyd]

How do you find the goingsuperfast Headers? Has it made a decent improvement in spool-up times and responsiveness?

[jcc911]

Beautiful car and engine! Too bad you were not in WI, I sure could use some help rebuilding my engine;-)

[porschett]

Originally posted by WydRyd
How do you find the goingsuperfast Headers? Has it made a decent improvement in spool-up times and responsiveness?

goingsuperfast.com. Albert is your man. But the IC maybe a tight fit for a stock decklid/wing.

After a drive, I occasionally check the temps of the IC. The IC intake is is warm/hot to the touch. The IC outlet side is incredibly cool. As you move your hands from left to right, in the middle is where it starts to cool off and my tube to the TB is still cool!

[WydRyd]

What size is that IC? Nice

[porschett]

the IC is 26x12x3. You'll need to remove your A/C cooler from the wing and it won't clear the stock air box. If you're doing EFI, then the IC should be perfect fit with no clearance issues.

[rsrfan]

Very, very nice. You are using the k27 7006, correct?

JP

[porschett]

JP,

I recall the designation being a 7200? with an 11/11 somewhere in the tag. So I'm not really sure what it is. My guess is the stock C2 Turbo?

[RarlyL8]

Those are nice numbers!
Have you looked into the digital WUR now on the market? This engine would be a really good candidate and at ~$600 it won't hurt the wallet too much.

[porschett]

Hi Brian,

Actually, I'm looking to do some mods to my existing WUR in addition to being able to adjust the WUR spring pressure. Basically, I'm going to send boost pressure to the WUR only when RPM hits a certain range (i.e, 4000).

Only then will WUR start to dump more fuel. Stock function is as soon as the WUR sees any boost pressure (at any RPM), it'll dump fuel (alot!) immediately. If I can delay the additonal fuel dumping until 4000 (or 4200 according to the AFR dyno reading), then I won't be affected by an over rich condition (<10 AFR!) at low RPM.

How am I going to accomplish this? Well, Leask Engineering (bleask@cox.net) has it in development and so far it looks really promissing. The benefits are as follows:

- No over rich condition at low RPM
- No fouling of plugs
- No fuel contamination in engine oil
- Most importantly, more mid range torque -> more top end HP!

[RarlyL8]

Instead of dumping fuel beginning at a specific RPM why not dump fuel at a specified boost level (such as 0.3bar)? A steet car often runs partial boost at all RPMs in various driving situations. (I don't know if this is better for a street car, I'm just throwing the idea out there)

Either way I am looking into an adjustable and flexible WUR, mechanical or digital, for our application. EFI is great but still too expensive in my opinion.

[porschett]

Yeah, dumping on boost level is prefered, but I don't know a way to trigger the fuel dump on a function of boost. Unless the digital WUR does the job. I'm in the same boat as you...EFI is the way to go, but too expensive.

BTW, who makes the digital WUR? I saw their ad in Excellence, but can't dig it up.