bogey1

gmonsen: whats a CIS velocity stack? My car is right at the limits of CIS (409RWHP) from what I understand and I worry about detonation. Please enlighten me when you get a chance.

gmonsen

bogey1: I'm not knowledgeable on Porsche motors yet, but I understand it to be a "velocity" stack with a diaphram in it. As air flow increases, the diaphram is pushed down. When its at max flow and the diaphram is all the way down, the CIS sets the injectors to max duty cycle. This seems like its performing a function similar to an airflow sensor. The issue is that past that point of flow you will be going lean and there's nothing the CIS can do to compensate for it. (If this is not a complete or accurate explanation, it's because it is all I know. I am trying to learn more, but perhaps someone else can augment this.)

Gordon

Sameer

The euro cis is good upto 470-480bhp. However for added safety many put in fuel enrichments like andial fec.

Jean,
with all those mods does'nt your boost crrep up closer to 1.1 bar or does it stay rock solid at 1 bar?
By the way I'm looking at the write up for your car right now in the magazine..looks great.

L8Apex

Congrats! Post some pics of the engine bay and turbo when ya get a chance. THX

Jean

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Sameer:
<strong>Jean,
with all those mods does'nt your boost crrep up closer to 1.1 bar or does it stay rock solid at 1 bar? </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Sameer, I could not tell you as I only have the standard digital boost guage, and it reads 0.7 bar max(it stays stuck there for a while though!).

Sameer

Jean you should get the 934 style boost gauge which replaces the clock and reads upto 1.5 bar. You dont want to be running more than 1.1 bar for a long run,,short burst is fine. With my mods and 1 bar spring, my boost creeped upto 1.1 bar so I decided to go for a 0.9 spring to play safe. Noe it just goes a tad bit under 1 bar on higher gears.

gmonsen

Jean and Sameer,

I sent a private message to Jean, but it hasn't been read, so perhaps I should put it here. Guys, everytime I check the forum, I go to this thread if there has been a new post. If its just the two of you talking about things, then I have wasted a bit of time needlessly. Perhaps you could start a new thread or continue the discussion offline? Not a big thing. Just a minor inconvenience. Thanks, Gordon

Sameer

Gordon,
My sincere apoligies.

Jean

Gordon

You're absolutely right, apologies to the board as well.
Cheers

gmonsen

Jean and Sameer,

Thanks. On the boost control issue. I notice that there's not a lot of discussion on this forum about aftermarket wastegates (TiAL) and intelligent boost controllers (Apexi/HKS, etc) or aftermarket comlete engine management systems and am a bit surprised. Obviously, the motors are quite robust. However, controlling the boost via a stepper motor in conjunction with either an aftermarket fuel controller or full EMS and bigger injectors, and bigger fuel pump would allow you to have much more specific air fuel ratios for more safety and more power. Is this more common than it appears? -Gordon

Jean

Gordon,

You will find several threads on the 911 turbo forum on this issue. Run a couple of searches there under "boost controller" for example. I am not an expert, but from what I gather,in general these modifications (electronic boost controllers) are more commonly done on Japanese cars for sprints and 0-60s, not the purpose of a P-Car, however several 911 turbos have them as well and seem to be succesful.
I am sure that Stephen of Imagineauto, Steve Weiner or Adrian to name a few of the gurus can help you out.
Good luck.

gmonsen

Thanks, I'll check the archives. As an Rx7 owner, I can vouch that these mods are de rigeur with these cars. However, the reason they are done is that the controllers let you set and control the boost specifically according to rpm and other factors, as opposed to just letting the mechanical spring handle it. I don't do it for any particular type of performance. Its across the board. I only do road racing with my car, rather than drag racing. Detonation occurs most readily at peak cylinder pressure, which equates to where your torque peak is generally. You want to be careful to run very safe boost levels there, but can push boost quite a bit before and after that without causing detonation, as long as you have the air fuel ratios mapped correctly for the boost you run. In general I find there's a lot of power untapped that you can get from running an aftermarket ems. I'll check out past threads and see what is done with the Porsche motors. -Gordon

fc-racer

Gordon,

Many of us who grew up on Japanese cars are running electronic boost controllers. I run the HKS EVC IV and love the unit. It works great and adjusts itself based on atmospheric conditions, etc. Come hell or high water, my car is always running 1.05bar boost at peak torque.

As far as EMS or aftermarket add ons like the HKS additional injector controller or the Greddy unit, it would make good sense since we already have an additional injector for the warm up system, however since there is already the system in place, it's easier to just buy the Andial or Rice kit to piggy back on the warm up system.

The biggest problem with the 964 Turbo cars is that they are K-Jetronic. I love the shape of these cars, I love the RWD, but I hate the K-Jetronic. It seems to be quite variable and not consistent enough for a turbo car. You need to dump in tons of fuel to keep everything happy and your mileage suffers. The Twin Turbo I borrowed had so much better mileage than my car, even though I was driving it within an inch of its life for the entire weekend.

The ideal situation would be to adapt the Motronic system to the 964 Turbo, that would give ultimate driveability, parts availability and ease of use. It would however not be as flexible as a Motec or Autronics, etc. because the coding software is harder to get for the Bosch units.

Does anyone know if there is a plug and play (as much as it can be given that you have to change the intake manifold, etc.) Motronic setup for our cars?

I thought RUF might have something since they built their business on EMS turbo cars, but even they just go the easy route and plop a big turbo onto this car and add some fuel.

fc-racer

gmonsen

Fc: I wonder why I couldn't just install a Motec or AEM and dump the Jetronic? The whole deal is just the rewiring/new harness. The easy way to do it and retain the stock system is to essentially run the standalone EMS in a sort of parallel mode with the existing system. What you do is just disconnect the fuel injector leads and ignition leads. You need to collect the rpm reading off the tach directly or through the K-Jetronic, if it has an output. Splice into the existing flywheel magnetic pickup(or install a crank angle sensor). The stock ems still gets all the current signals from the sensors, but doesn't control the fuel injectors or coils. The new systyem does. Several of the newer MoTec and AEM systems can directly control boost or you add the HKS or Apexi units with a good-sized TiAL wastegate and you're there. Done this way, you don't have to build an entirely new wiring harness, though there is some redudnacy. I think I would want to keep the original system in place. Anyway, this works. Baswic cost without tuning for the EMS is $1250-3000. The separate boost controller is $400-600 or so...

That way, as you know, you control the AFR's and boost completely. I have a wideband Lambda and would use it to set the Fuel.

Gordon

fc-racer

Gordon,

The problem with this car is that there is very little that is electronically controlled. Basically, the ignition is about it. The rest is mechanical. Even the factory boost control is completely based on the wastegate spring.

You will have to install most sensors yourself and fabricate mounts, etc, etc. Also, the injectors that are run on this car are designed to run continuously.

I have very little knowledge of how the CIS system works, but guys like Stephan from Imagine have a wealth of experience and can probably chime in.