srf506

Chet,
Would seem to make perfect sense, whether its forced induction or NA, any improvement in volumetric efficiency in a motor is a good thing. They're basically air pumps so increasing the volume of air you can pull into the cylinder allows you to burn more gas which them makes more power. Other little tricks, like swirling the flow and etc would just improve on that. As long as you can keep the thermal properties under control so you're not frying pistons or valves, and timing has enough to get you the anti-knock you need why not? Good luck with it and keep us posted how it does as you drive it around.

chet 77 930

Dead on......

special tool

YES cost is not a consideration for someone who wants to push a 930!

Pushing with CIS is crazy, in my opinion.
The cis is fine with 260 US HP, but these engines are a little too expensive to wreck when you push.

I probably wouldn't even push a 930 WITH EFI, but I am a conservative guy.

PorschePhD

Cough-cough-bull-cough-s*#@t-cough

nathanUK '81 930 G50

Chet, shame about your PW.

I think the Kpa is the same as bar, except that you -1 from the reading. eg 1.9Kpa is 0.9bar.
1.0Kpa is 0bar.
.5Kpa is -0.5bar.

Just a guess though. I guess you could google it.

chet 77 930

PW? Its been a long day for me today but you lost me.....

RarlyL8

CIS is capable of producing in-spec A/F ratios up to ~400HP at the rear wheels throughout the RPM range when properly tuned. Beyond that the CIS modifications needed to retain proper A/F ratios become diminishing returns.
There is no doubt that Chet's engine has benefitted from EFI but it also got there with CIS, the ragged edge yes, but it got there. Backing off the boost a smudge and further tuning would have proven reliable and passed smog.
Building an ultra high powered 930 engine will take EFI. Hitting those numbers with a 3.0L is a home run. Nice job!

chet 77 930

Thanks!

JBL930

Fair point, but then there isn't a sane person in Warrington so you can't comment


Chet, thanks for the explanation, I was under the impression that a standard K27 could only get somewhere IRO 400fwhp in a 3.3 at 1bar. My heads have been ported, by the Ninemeister, along with other normal mods and a BB 9m turbo and 1bar got me 497bhp
I’m curious as to what boost you were running in a 3.0ltr with a standard K27 to get 440rwhp on CIS, good job

A.Wayne

There is no comparsion between a CIS car and a efi CAR .. the cis car will have more lag , smaller T/Q curve and poor Throttle response, while the peak numbers are close , the cis car will be slower, it might feel faster as the nothing then everything feel , but line both cars up 2nd gear roll on and watch the efi car go away.. also a cis car making 400 whp vs efi at the same power , the cis car will have less reliabilty.
Have to say , i have never seen a converted cis car to efi make less or the same power, the efi one is always higher ..now a cis car making 400 whp at
13:8 A/F is not the same as 400 whp @ 11:9 A/F , the leaner engine will not have any power after one run thru the gears .

PorschePhD

Bingo. People don't realize this nor do they understand. A car that can make the same power with EFI with a 2 point lower AFR taking into account this puts it in the safe range and you do it with less boost you are still gaining a better TQ curve and overall power under the curve. The 10AFR dip under boost is gone and the cars band becomes more linear. The more you hammer the 13.8 AFR car each run the combustion temperatures continue to go up and up without any ablity to adjust for that. An EFI car can control it.

So people have to ask when their cars are running 14s and maxed out which is more expensive, the EFI or the CIS with an engine build. Not everyone needs it and if you are happy with your HP and it is in a safe range then you can take or leave it. Bottom line is Chet's car while it made GREAT HP for a 3.0 it was a time bomb waiting to happen. Not if....just when. Those kind of numbers are not uncommon for a 3.4 build we do, but not a 3.0. Period.

Now his car has a better power band, makes the same power but with less boost and carries a 11.7-11.9 at WOT full boost and redline. Perfect. It did not do that before.

chet 77 930

The power output prior to was unusually high for 3.0 motor to begin. Looking at these results and thinking back to the homework I did before building the motor, I think this case is one where the maximum VE has already been reached given a 3.0 displacement in this current configuration. I could pick up a little more torque here or there with a couple more bolt ons (headers, intake manifold etc) but for bigger gains it would need changes to some internal things like piston size, port sizes again etc.

nathanUK '81 930 G50

Chet, PW is short for "password".

Thanks for posting about the conversion.

chet 77 930

Thanks Nate...

RarlyL8

I guess you all think I am an idiot.
I am very aware of how A/F ratios affect performance and engine longevity. CIS is capable of 12.0-12.2 A/F ON BOOST at 400+ HP WHEN PROPERLY TUNED. Who said anything about 13.8? That would be REDICULOUS.
I guess the real issue is that nobody knows how to tune CIS.