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CIS Horsepower

I've seen Eddy Bello's cars pulling wheelies and putting down 1289RWHP; I've seen some guy on YouTube with an '89 slope-nose 3.4 putting down 733RWHP; but these engines were EFI-ed to the maximum - what's the most anybody has (safely) got out of CIS?

Did somebody mention Brent930, back in the day, getting 450RWHP? (Think my old tub is about 315RWHP.)
Old 11-19-2009, 10:47 AM
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Originally Posted by tj930 View Post
I've seen Eddy Bello's cars pulling wheelies and putting down 1289RWHP; I've seen some guy on YouTube with an '89 slope-nose 3.4 putting down 733RWHP; but these engines were EFI-ed to the maximum - what's the most anybody has (safely) got out of CIS?

Did somebody mention Brent930, back in the day, getting 450RWHP? (Think my old tub is about 315RWHP.)
Impossible to answer. CIS simply dumps fuel under full throttle. You can technically make it dump as much fuel as you need if you open up the system to flow enough gas. But it just becomes less and less accurate the more power you are making, you would just end up dumping literally gallons of fuel to feed a big powerful engine.

It is just so imprecise and sloppy above 4-500 hp that it becomes a really stupid way to proceed. Your car would be pig rich to the point of oxygen starvation on boost onset and then when it cleared out you would be straight into massive horsepower. It would increase turbo lag.

The driveability would suck.
Old 11-19-2009, 11:30 AM
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Originally Posted by tj930 View Post
Did somebody mention Brent930, back in the day, getting 450RWHP? (Think my old tub is about 315RWHP.)
Do a search on 'Brent 930' and you'll find plenty of info. He got to 450+ RWHP with plenty of work, tuning and cutting edge (at the time) modifications.

DonE before he went EFI, was also pretty far 'up there' on CIS.

Also do a search on 'CIS' and you'll find several long discussions.
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Last edited by WinRice; 11-19-2009 at 12:06 PM.. Reason: Added info
Old 11-19-2009, 11:54 AM
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Honestly you can buy the brains for a solid efi set up for under two grand, anybody looking for 500 hp+ can afford to upgrade.

Forgot to mention, ten foot long flames coming out your tail pipe is really not as cool as it sounds in everyday traffic.
Old 11-19-2009, 12:32 PM
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Honestly you can buy the brains for a solid efi set up for under two grand, anybody looking for 500 hp+ can afford to upgrade.

Forgot to mention, ten foot long flames coming out your tail pipe is really not as cool as it sounds in everyday traffic.
After pushing the limits of my CIS, I have to agree with DDDD. That's the reason I've been slowly collecting EFI parts.

Recently, drmatera put together a budget EFI setup.
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Old 11-19-2009, 01:05 PM
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Back in the day, Brent and I challenged each other to build the biggest HP on CIS. We both hit a wall when it came to controlling spark with the stock system - it can't be optimized. You need an aftermarket spark system. We did everything from head work, extrude honing in the intake, timing the cams, headers, half a dozen different turbos, tweaking the WUR on three axis and so on. We were getting between 425 and 450 RWHP. Those are big numbers for CIS.

But this leads me back a big problem with CIS - you can't control spark. For the most part, I really don't care about total HP. I care about torque. Using an ECU, I can control spark (timing) and can tune in lots of torque much earlier than any CIS car. From a dead stop or pulling hard out of turn 7 at Road Atlanta, I want torque. My car puts out 525 rwhp, but it also lays down nearly 500 ft lbs of torque early in the power band. Thats the kick in seat of the car you feel in my car...
Old 11-19-2009, 06:43 PM
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Here is a thread on a 620hp CIS Monster: Cis monster

Optimizing the ignition on a 930 seems to be a solid opportunity for increased throttle response.

Would love to see someone properly set up one of the newer programmable MSD units on a CIS 930. However, dependable AFR's and compensation for changes in environmental factors become important variables when one wants to run closer to optimized settings and that is a CIS is weakness.


Brent had Andial re-curve and modify his ignition system. He did have the intake manifold honed but kept his intake ports stock size. He had all the normal goodies (SC cams Kolen IC, early HF turbo, shortie headers...) plus thermal coatings. I talked his CIS head builder into adjusting it for more fuel which later led to the HF fuel head. This allowed him to push the CIS HP limit some. I believe he also tipped above the one bar range on some of his dyno runs if I recall correctly.
Old 11-20-2009, 07:45 AM
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CIS has nothing to do with spark. EFI also should have nothing to do with spark if you wish to accurately compare. Often this is the case when arguing the merrits of EFI. If you take spark out of the equasion the functional gap between CIS and EFI is reduced. That fact tells you how important timing control is to driveability.

CIS is a component system so you can change or mod the components to support just about any horsepower level desired. If the posted question is "how much HP can the stock configuration CIS support" then the above figure of ~450whp is the answer. 400whp is common, that last 50 takes a lot of work.
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Old 11-20-2009, 09:48 AM
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Quote:
Originally Posted by RarlyL8 View Post
[snip[ If the posted question is "how much HP can the stock configuration CIS support" then the above figure of ~450whp is the answer. 400whp is common, that last 50 takes a lot of work.
And a lot of money....

And when you're done, and at that level, you still have a CIS car (aka, Frankenstein). On the other hand, if you keep the HP in the 375 - 400 hp range, you have a reliable, very fast German go-cart that's hard to beat in many aspects.

Last edited by DonE; 11-20-2009 at 05:14 PM..
Old 11-20-2009, 05:11 PM
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Old 11-20-2009, 08:30 PM
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Modifying the car with the tried and tested usual mods i agree 400 WHP is acheivable if the car is then set up properly!..I believe the fuel is available for slightly more power but it does take a little more effort and expenditure!
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Old 11-21-2009, 11:18 AM
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My two cents worth.

I suspect that getting enough fuel for 400rwhp/470fwhp takes a lot of effort.

3.3 CIS turbo motors were built to supply at its best (special wishes 3.3 S) about 280rwhp/330fwhp.

It requires over 55% more fuel delivery than stock to get to 470fwhp.

By fattening CO I suspect we can stretch the stock fuel system up to about 340rwhp/400fwhp at is best.

After that significantly reducing control pressure can support about another 10%or so more HP.

Then, modifying the fuel heads delivery capacity can add about another 10% or so and still be a pretty tunable car. More that that and things start to get on the wild side.

Thus, I suspect that 400rwhp/470fwhp would probably require both modified control pressure settings & modified head. Past that is getting out there though it can very well be done.

Of course, it all depends on the efficiency of the motor and the dyno used as most seem to read higher than the German sized horses that the factory used.

Example. My stock 85 3.2 w cat bypass and chip pulled 215rwhp/253fwhp for a car that is rated about 205-231 (euro) fwhp by Porsche.
Old 11-21-2009, 01:58 PM
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Keith, your assumption is accurate. 400whp takes a fuel head mod, adjustable WUR and fuel pressure increase. Not difficult just tuning. Above that gets tricky as the tuning starts to fall apart on the low end.
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Old 11-21-2009, 08:58 PM
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Quote:
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My two cents worth.

I suspect that getting enough fuel for 400rwhp/470fwhp takes a lot of effort.

3.3 CIS turbo motors were built to supply at its best (special wishes 3.3 S) about 280rwhp/330fwhp.

It requires over 55% more fuel delivery than stock to get to 470fwhp.

By fattening CO I suspect we can stretch the stock fuel system up to about 340rwhp/400fwhp at is best.

After that significantly reducing control pressure can support about another 10%or so more HP.

.
My 2 cents experience

Use up graded fuel pumps and increase fuel pressure is the easiest way to get more fuel with CIS setup .

Considering the fuel flow capability, the CIS head is not a limit. It can flow huge amount of fuel..... But the stock injectors are the limit and the restriction. By using the injectors of the 3.6T, you can really get a huge amount of fuel. The problem will be to deal with low RPM.
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Old 11-22-2009, 07:27 AM
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I would like to see a flow test compairing the 3.3 & 3.6 injectors. Untill then I must remain a bit suspect.

CIS injectors are not like EFI injectors. I suspect that if the 3.6T injectors are bigger, then they would still flow the same fuel at most the rpm but could alow more fuel up top so they should not cause any tuning issues.

I suspect the way to more fuel through the CIS system is more system pressure and a fuel pump that suports this at some point would become a requirement. With the right pump it might be possable to put a fuel pressure reg (rising rate?) in line on the return line to effect fuel flow. However, the WUR return line would probably have to have its own path to the gas tank.

I belive of the main ways the 3.6T gets more fuel is a different WUR that runs lower control pressure on boost to support its 360HP.

I wonder if the 3.6T metering cone is any differant as to profile than the 3.3's to accomidate the 10% higher air flows?

If one was to go to the real dark side with CIS it would be interesting to use a V8 fuel head and plumb the extra two injectors in before the throtle plate. It would require a significant increase in control pressure or a reduction in the windage of the metering plate by cliping.
Old 11-22-2009, 08:46 AM
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Quote:
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I would like to see a flow test compairing the 3.3 & 3.6 injectors. Untill then I must remain a bit suspect.

CIS injectors are not like EFI injectors. I suspect that if the 3.6T injectors are bigger, then they would still flow the same fuel at most the rpm but could alow more fuel up top so they should not cause any tuning issues.

I suspect the way to more fuel through the CIS system is more system pressure and a fuel pump that suports this at some point would become a requirement. With the right pump it might be possable to put a fuel pressure reg (rising rate?) in line on the return line to effect fuel flow. However, the WUR return line would probably have to have its own path to the gas tank.

I belive of the main ways the 3.6T gets more fuel is a different WUR that runs lower control pressure on boost to support its 360HP.

I wonder if the 3.6T metering cone is any differant as to profile than the 3.3's to accomidate the 10% higher air flows?

If one was to go to the real dark side with CIS it would be interesting to use a V8 fuel head and plumb the extra two injectors in before the throtle plate. It would require a significant increase in control pressure or a reduction in the windage of the metering plate by cliping.
Hello Keith

The metering cone on the 3.6T is larger than 3.3 T....do you believe it ? So for the same air flow , the metering plate moves less !

The wur of the 3.6 T provides higher control pressure than the 3.3T...

But 3.6T injectors have much higher flow !

Conclusion: Porsche use higher flow injector for the 3.6T. In order to control these larger injector at low RPM, they increased the metering cone OD and they increased the control pressure.
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Old 11-22-2009, 09:01 AM
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In my experience the standard "EURO" fuel head with just an increase in system pressure can produce enough fuel to acheive 400+ RWHP and with the correct tuning can be controlled also
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Last edited by stup; 11-22-2009 at 10:10 AM..
Old 11-22-2009, 10:07 AM
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When I had CIS, I could set the AFR to 10:1 and a bit lower if I wanted. This was with my Euro fuel system, my own WUR modifications and 425 RWHP (stock fuel pumps are just fine, in fact I use them on my EFI system). Fueling wasn't the problem - I couldn't get enough air into the cylinders. I even modified the air metering plate stop pin to let more air in, but no good.
Old 11-22-2009, 10:41 AM
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"Fueling wasn't the problem - I couldn't get enough air into the cylinders. I even modified the air metering plate stop pin to let more air in, but no good."

Did you replace the steel down pipe that is squished where it goes around motor mount with something with a bigger diameter?
Also did you open up the intake ports, injector blocks, and intake maifold ports to something bgger than the choked down 32mm?
Old 11-22-2009, 11:44 AM
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Quote:
Originally Posted by DDDD View Post
Forgot to mention, ten foot long flames coming out your tail pipe is really not as cool as it sounds in everyday traffic.
Looks pretty cool to me ...



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Old 11-22-2009, 12:37 PM
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