special tool

There are guys on this thread who could write a book on CIS.
What is the highest HP YOU PERSONALLY (not your mechanic) have extracted from a CIS-equiped 930?
Please show the dyno with AFR.
And we are talking WHEEL HP here.

PorschePhD

That is an absurd statement. You mean YOU wouldn't know how to tune it. I have made 433RWHP on a C2T with CIS and a 12.1 AFR. But that is still expensive. Chet’s car is a 3.0 making what 3.4as do. Do the math, it would have to be out of fuel. We have mentioned 12 times in this thread about the car being a time bomb.

RarlyL8

I'm glad we agree it can be done.

If you read my statements carefully you will see that is all I said - it can be done.

Seems I touched a nerve on the CIS vs EFI non-debate. I completely stand by the statement that most folks don't know the capabilities of CIS. There are several new and inovative CIS components on the market that greatly enhance fuel metering and delivery. I beleive iA even sells some of these products.

And yes, as a matter of fact I do know how to get 400 rear wheel horsepower out of a CIS 3.3L 930 engine with proper A/F ratios. It's called and adjustable WUR. Some are digital. That's not all that is involved but it is a critical part.

As far as my personal dyno sheets are concerned, that was a strange request. What difference does it make who produces the proof? I beleive NASA made it to the moon even though I wasn't actually on the rocket myself to see it. Have you personally ran sid-by-side comparisons of properly set up CIS and EFI 930s?

Maybe Stephen can show you the dyno sheet from the C2T. That was 433HP.

Even with modern technology thrown at it, CIS will never rival the tunability and precision of EFI. That is the CIS vs EFI non-debate. EFI is better. If you desire your engine to head north of 400 RWHP (such as the engine owned by the author of this hijacked thread) then you have no options, EFI is the only reliable and safe way to get there. Below 400 RWHP you have options. CIS can deliver A/F ratios that are in spec throughout the rpm range.

special tool

Why is that a strange request, slim?
It validates you - you NEED to validate yourself when you accuse noone of knowing how to tune CIS.
Somehow I knew you'd come up empty.

A.Wayne

On a 3.3 930 with 4 spd trans and EFI , 400 whp is obtainable with 8-9 psi , you can pull away in top gear from 1100 rpm , replecate that with a CIS equiped car, would luv to see it


So no cis will not match EFI even at 400 Whp.. The dyno sheet request is valid as you claim such numbers and performance. it would be interesting to compare curves .

RarlyL8

No, "I" do not have to validate anything.
Go back and read my words. Don't read between the lines, read the words.
My statement is simple: CIS can support 400 rear wheel horsepower with in-spec A/F ratios throughout the rpm range.
I said nothing about comparative boost figures or lag or anything else for that matter. Pure and simple. CIS can properly support 400RWHP. Period.

The statement about no one knowing how to tune CIS was meant to get the attention of those that do know how. They tend to sit on the fence and say nothing while the think-they-know-it-alls have a field day. Well it worked. I know that Stephen knows CIS can properly support 400HP throughout the power band. I also know he has done it in the past with the C2T and other 930s, and I know he backs up everything with dyno runs. That alone should be validation enough.

Frankly I don't give a damn if you put EFI on your lawn mower. Your business, your money. It's no wonder this sight has so little traffic if you treat other occasional posters in the same manner. My comments were not meant to be caustic, only to spark discussion on how the author achieved 433RWHP on CIS and why he made the switch to EFI.

A.Wayne

Same here. iI Believe this was answered in spades on the efi side. . You seem to have a hangup on the change , so my question still stands, Do you have a 930 with cis making 400 whp.? if so , how did you achieve this ?

RarlyL8

How this is achieved has been discussed in several places. Stephen has done it, Brian Leask has done it, and others who are here on this board.
I did not develop the methods and equipment and take credit for nothing. What I have done personally is to apply these methods to my own application.
Chet obviously has a lot of knowledge concerning CIS and with Stephen's assistance was able to get his 3.0L engine waaaaaay past where others have gone with CIS. What I posted previously was that if he pulled the engine back to 400HP he could achieve the goals of passing smog and engine longevity while retaining CIS - something he likely already knew. My missunderstanding was that these were not his only goals. He wanted huge power, not just big power, and we all agree that CIS will not support that.
Unfortunately I came in on the end of Chet's quest for 3.0L 930 supremicy. I did not know the history or all of the goals and was playing catch up in one thread.

To directly answer your question, an adjustable WUR is the key to achieving A/F ratios that are in-spec across the rpm range for a 930 producing 400 or less rear wheel horse power. There are several different types on the market, digital, mechanical, hobbs switch activated, etc. How do I know they work? I know fellow enthusiasts who are using these components in conjunction with the other mods needed to achieve 400HP. They have the dyno sheets. My engine does not have ported heads and therefore is not capable of achieving that mark. Does the fact that my engine is not built to 400HP change the fact that a proper A/F ratio is achievable with CIS at those levels? No. Do you need data to back it up? Yes, but anyone can post a dyno sheet. You need data from someone you personally trust. That is where I got my data.

Sorry Chet for the derailment of your thread. You've performed a great feat with your 3.0L and I applaud you for it.

DDD

Chet,

Why did you choose Stephen's EFI product out of all that are available? Does it have advantages that you liked over other systems?

What were the other systems that you seriously looked into, and why didn't you go with them?


There are so many products out there......

NineMeister

Any EFI system is only as good as the guy who programs it, so a cheap system fitted by an experienced installer/tuner will probably have better results than an expensive system badly installed & mapped. In other words, choose carefully and base your choice on all factors, not just price or convenience - I suspect this is what led Chet to make his choice.

slownrusty

Wise words!

chet 77 930

I'm back...was out working the last couple of days.

Lol..I can see there was a little discussion going on. In the end we all win anyway....we're the fortunate ones who get to drive these cool cars. Thanks for your input Rarly8, its well appreciated.
As I mentioned earlier, this is an EFI case that had a little different intention for converting. Stephen and I talked about this well before the decision was made to have the work done. We spoke about the goals, hardware/software to get there and most importantly for me as Nine Meister mentioned....who the tuner was going to be.
One thing I constantly keep forgetting to mention in terms of porting which I feel plays a big part of the hp increase.....the cylinder heads on a 76-77 930 have a littler larger exhaust ports than the 78 on 930's. And because of this, porting the intakes alone on the earlier head should (mathematically anyway, I’ve never actually measured it on a bench flow) generate better air flow into and out of the cylinders than the same port job on a standard 3.3 head. I suspect Porsche closed them slightly on the 3.3 motor to increase exhaust port velocity and reduce some of the turbo lag that was very prevalent in the 3.0 turbo's.

Tom F

Chet, this is certainly one of the more interesting threads I've seen on Rennlist in a while. I hope that you'll fill us in on the port work that you did. (Photos?) Stephen's and your work on the 3.0 has been an inspiration to those of us who are still on the steep part of the learning curve.

JBL930

Chet, if you don't mind, what boost were you running before the EFI conversion to get those figures?

chet 77 930

My factory tachometer boost guage in the car was showing 1 Bar and wasnt going over. There was more room to crank it up but I kept reading the plugs every few days or so ( they were perfect) and there wasnt enough fuel to justify doing so. I think Stephens equipment registered about 1.1 or 1.2.

Tom...I have no problem sharing, but to be honest I did those heads a little over 4 years ago and will have to recollect exactly what I did. I can tell you that the math I used to calculate the port size gave me an answer of 37 mm on the intakes. I had to have the heads flycut to get 7 to 1 compression to work with the ports. A little higher would have been more ideal. And the cam spec I used was the stock 911SC grind. I have them set at 1.75 mm (new chains) initally which are probably now 1.6 or so with the chain stretch. I do remember blending the 37 mm into the port and was very careful to not have polished ports although I did clean the bowl areas up a little. Again, this combo worked in conjunction with a little bigger exhaust ports too (34mm I think? Dont remember exactly). I have 89 930 OEM heat exchangers which if I remember correctly are about 35mm. I'm almost sure that if this size is increased it will have a negative effect on the drivability in terms of low end torque.

I had a second exhaust pipe added to the muffler a few weeks ago. Doing so actually decreased the cylinder velocity and resulted in a low end torque loss. You could actually feel the difference. It helped a little in the upper RPM range but not enough to justify the lower rpms loss and not to mention the increased noise resonance inside the car. I have since had it welded back up. I kept the pipe in place because it looks cool but its no longer open.