Dyno results

[emcon5]

Just got back from the dyno:




Three runs, essentially the same results each time. I expected more power, but I realize that dyno numbers are a little subjective. On this dyno, on this day, my car made 174HP at the wheels, call it ~205 at the crank.

Frankly, I care less about the power output as I do about the AFR. With 98mm bore and 964 cams I was a little concerned about the stock CIS being able to deliver enough fuel, but ~12.2:1 at 6500RPM is not lean at all, it is a little rich.

I am a little concerned at the RPM figures, I shut down at 6.5K on the tach each run, but their graph shows almost 6800. Looks like my tach may be off.

The dyno place was ATP Turbo in Fremont, 3 runs for $65. http://www.atpturbo.com

Tom

[Early_S_Man]

Tom,

Looks good, espaecially that A/F ratio at 6500 rpm! Don't want to see any 15s, 16s, or 17s up there

You might want to get a digital multimeter with clamp-on probe and rpm function to check that tach! Steady state it may be OK, but it's those delta-t delays in response that get you every time!

[Elombard]

So this is a SS 3.2 with CIS and 964 cams. Which Exhaust SSI? I would have hoped for a little more grunt also, does it feel good on the road
:-))

[911ctS]

Are you running the Max Moritz big bore kit on a basicly stock 3.0L and 964 cams with CIS??? Im very interested in what your engine is.

[emcon5]

82 911SC, rebuilt at 111K miles due to excessive oil consumption, has 115K on it now.
98MM Mahle Cylinders with RSR Pistons, measured at 9.8:1 CR.
Cam reground to 964 profile by Elgin.
Twin plug with Rennsport 964 distributor conversion, 2 Bosch CDIs and coils.
ARP rod bolts, 993 steel head studs.
SSIs with a Dansk muffler.
Stock CIS system.

Noah, I can't complain about the peak torque, but I was expecting a flatter torque curve like yours. Your peak torque comes 1000RPMs higher than mine. BTW, it is about time you got a readable scan of that damn dyno sheet.

I wonder if my smaller intake ports/runners are hurting me.

It pulls like a freight train.

Tom

[Chuck Moreland]

I think 205 is respectable. Compare to a 3.2 Carrera that has a better intake, heads, and EFI - makes 207hp or 215hp depending on year.

You're right in there. And your car DOES pull strong. Your torque curve is amazingly flat which makes the car easy to drive fast.

[911ctS]

I bet your small ports are hurting your peak power. Your torque curve is huge though. I bet if you swaped out your heads for the early 78/79 39mm intake port heads you'd be at 200 hp easy, and not sacrifice any torque. You may loose some low low end torque between 2k and 3K but not much.

Hopefully jluetjen will chime in, he knows alot about what heads are ideal for each engine.

[dd74]

Looks a little like my hp/torque curve. My engine's stock, though, except for '74 heat exchangers and a Triad dual-in-dual-out. I believe the similarities have to do with the small intakes and ports we both have. Sure is nice to have torque, though.

[beepbeep]

Very nice torque, now how about opened up intake ports and tbitz EFI? should give 15HP out of the box...

[Steve@Rennsport]

Hi Tom:

Lookin' good, Sir. That nice fat torque curve is the result of displacement, compression and twin-ignition,...

As you said, your AFR's are a tad on the rich side; something quite unusual for a CIS engine with higher than normal compression but its very consistent. If you wanted to go to the trouble, you would pick up a bit more HP with peak AFR's between 13:1 and 13.2:1

[emcon5]

Originally posted by beepbeep
Very nice torque, now how about opened up intake ports and tbitz EFI? should give 15HP out of the box...

That is somethnig I have been thinking about, but it is a long way down the road. I have valve clearance with the RSR pistons, so if this happens, I will change the cams too, probably early "S". I wouldn't mind sacraficing a little torque for more top end, and with that combo I would be close to 3.6 power, but with the early engine character.

My thought is to keep my eyes open for a set of 84-89 heads and induction. Like I said, that is way down the road, for the moment I still have to deal with CA smog.

Originally posted by Steve@Rennsport
Lookin' good, Sir. That nice fat torque curve is the result of displacement, compression and twin-ignition,...

Thank you Steve, I couldn't have done this without your help and advice, not to mention your milling machine

As you said, your AFR's are a tad on the rich side; something quite unusual for a CIS engine with higher than normal compression but its very consistent.

I was pleasantly suprised. From looking at some other CIS dyno sheets, I was expecting it to jump around a bit, but it essentially flat from 4500RPM up. I certainly didn't expect it to be richer at 6000rpm than at 3000. My AFR is considerably more stable than some 3.6 charts that have been posted, Jack's, for instance. Pretty amazing for 30+ year old technology on an engine it wasn't designed for. Cheers to Bosch.

If you wanted to go to the trouble, you would pick up a bit more HP with peak AFR's between 13:1 and 13.2:1

Time for the cerimonial Peppering Steve With Still More Questions

What do you mean by "a bit more HP"?

In your opinion, could the small ports/runners be why it runs out of steam up top (compared to Noah's engine)?

Do you think a different muffler would do anything for me, and if so, at what RPM range?

Thanks,

Tom

[kstylianos]

Tom,

As another comparison, here is my recent dyno chart. 82SC 3.0 liter, 9.8:1 CR JE's, single plugged with Elgin SC330 cams, SSI's and Dansk sport exhaust. The early 80's intake ports and runners were opened up to 36mm. It's interesting to see the max torque numbers and curve are fairly identical and the HP curves are also VERY close. I think this is also an interesting comparison between 964 and SC330 cams.

Your worries were the same as mine...the CIS would not be able to deliver enough fuel to keep the AFR in safe place. Our AFR curves are also quite similar. I'm in the process of smoothing and leaning out the AFR to Steve's recommended 13.2. See enlarged AFR chart below.

BTW: My max advance at Dyno time was close to 38 BTDC (scary). After I brought it back down to stock, there was a noticeable performance decrease.

Keep us posted, this is good stuff.....

[Lorenfb]

Your average AFR is right on, i.e. it should be 12.6 for max torque. The problem
you'll have is to further optimize it and prevent the swings above and below 12.6.
This is very difficult without some form of feedback. If you lean the upper (above
4000), you'll be very lean below causing lost torque below 4000.

[beepbeep]

My understanding is that CIS main problem isn't fuel-delivery itself (it can spray heaps of fuel as it's constantly open) but the fact that it's plunger is a huge obstacle in the airpath.

[911ctS]

Originally posted by beepbeep
My understanding is that CIS main problem isn't fuel-delivery itself (it can spray heaps of fuel as it's constantly open) but the fact that it's plunger is a huge obstacle in the airpath.

I think your right on. When you upgrade to hotter cams with more overlap the CIS can't handle the extreme pulses that echo back up through the intake system. I would think that if you had anything wilder than 964 cams the sensing plate would start dancing around and fool with your AFR.
This is why Porsche made the SC cams with negative ovelap.

[emcon5]

Originally posted by kstylianos
As another comparison, here is my recent dyno chart. 82SC 3.0 liter, 9.8:1 CR JE's, single plugged with Elgin SC330 cams, SSI's and Dansk sport exhaust. The early 80's intake ports and runners were opened up to 36mm. It's interesting to see the max torque numbers and curve are fairly identical and the HP curves are also VERY close. I think this is also an interesting comparison between 964 and SC330 cams.

Charlie, The peak torque numbers are similar, but the big difference is your torque stays close to peak from 3900 to 5000 RPM, before it starts to drop. My peak comes ~100 rpm later, and by 5000rpm has already dropped off 10 ft lbs. With my larger displacement and hotter cam, I really expected a longer peak. Also looking at John L's calculations, peak torque for a 964 cam should come at ~4800RPM, mine was 4200. Then again, Noah has the same cam, and his peak was ~5200. Who knows.

I keep coming back to port size.

Originally posted by beepbeep
My understanding is that CIS main problem isn't fuel-delivery itself (it can spray heaps of fuel as it's constantly open) but the fact that it's plunger is a huge obstacle in the airpath.

Just to clarify: in principal, CIS can deliver enough fuel for any engine, assuming the system is designed to meet the engine's needs. My concern was that a fuel system designed to feed a 3L engine could safely feed a 3.2 L engine with higher compression and a hotter cam.

There are issues running high overlap cams with CIS due to the pulsing at low RPMs screwing with the sensor plate.

Tom

[twin plugged targa]

Hi emcon
I am surprised you are not pulling more hp at that compression rateing. I guess it is the cams?
I beleive that this less peaky high torque at low revs would be well suited to a hill climb car?.
Are track cars generally higher HP and more peaky?.
At 10.5 CR and 3.0 litre (hope thats correct?) are'nt RSR's pushing much higher hp?. Is this cams or a whole combo of fuel/air dellivery/exhausts etc.?
- Just seems I would have expected more HP out of that setup?
rgds Ben

[rpiper]

Is it possible that the dyno used was a Mustang dyno that gives resistance rather than a Dynojet dyno that does not? The Mustang dyno gives numbers about 12% lower than Dynojet. You should be making more hp with your setup. I have a 1978 3.0SC w/9.8:1 Euro p&cs, 964 cams and SSis and it makes 195 at the wheels with a cheapo Ansa 2 in 1 out (street), or 204 with headers and open exhaust (when it was in the race car). The I ran it on a Mustang dyno and hp was 177.

[kstylianos]

With my larger displacement and hotter cam, I really expected a longer peak. Also looking at John L's calculations, peak torque for a 964 cam should come at ~4800RPM, mine was 4200. Then again, Noah has the same cam, and his peak was ~5200. Who knows.

Where did you (Noah and other 964ers) time your cams? Max, min, or middle of the spec. Possible difference between the different peak torque curves.

Another player is the ignition timing advance curve, when it starts, its slope and max.

[Wil Ferch]

Sorry to keep bringing this up, but.
"Actual" hp , SAE hp, and Corrected SAE hp ( as the various graphs shoe here) are not the same. As an extreme example, actual hp might be the hp you calculate from the dyno run under "Actual" ( duh) ambient air conditions. Cold air, low altitude ( dense air), etc... yield high hp. And vice versa. SAE corrected hp does the same hp calc ( from measured torque) as does "Actual"...but corrects to some standard set of conditions that are useful when making comparisons...I think the default is sea-level ( 14.7 psia), 50% relative humidity and about 70 degF.
So let's make sure we're comparing apples...

Oh..and Mustang Dyno's will tend to read substantially lower than DynoJet 248c's.

--Wil Ferch