Looks like the CIS has got to go.....ugh

RSR Racer · 02-04-2022, 08:47 AM

While I have owned pcars since college, I have only been a member of the CIS fraternity for just under 2 years. It had been an educational experience! A close friend owns a shop and is a CIS guru. With his help, I am getting pretty familiar with it too.

After a full day of fuel system testing, tuning adjusting the WUR's enrichment pressure to as low as it would go, and some road tests (I'll skip the details since you guys have probably done all of this too), we confirmed that the CIS just cannot deliver the fuel needed by the current build. Even with the boost turned down to 0.7 bar, the AFR rockets past 13 at only 4800 rpm. Detonation happens next.

Not being one to spend money on making LESS power, we are starting to gather everything we need to go to a modern EFI system. With the supply chain issues these days, it is going to take a while to get everything but, if there is any interest, I will update the thread as we get started.

At least it runs well below 4500 rpm so will be out and about in it until it is time to pull the engine. Hoping to finish it by mid-summer of this year.

T77911S · 02-04-2022, 09:09 AM

what turbo do you have
what fuel distributor, cast iron or aluminum

what about your dist.
is your timing retarding once on boost.
are both ports connected on the dist.
do you still have the vaccum valves that control boost/vacuum to the dist.

RarlyL8 · RarlyL8's Garage

CIS can be modified to flow more fuel, your CIS mechanic should know that.
Yes EFI is more efficient and can support more power, decision to make that switch depends on your goals and budget.

RSR Racer · 02-05-2022, 11:59 AM

Its a '79 Euro with a few mods: 3.5 liter 7:1, ported heads and injector blocks to 36mm, twin plug, twin CDI w/old school 12 wire dist, headers, K27RSRaptor, DP intercooler, Jerry Woods cam grind, and probably more I am forgetting. No vacuum valve on dist, currently running 26 degrees at 6000 rpm.

Tested fuel pressure and volumetric flow rate to the fuel distributor and from the distributor. All tests exceeded specs. Fuel supply system appears to be good.

I have some experience with Motec and a little with AEM (still learning that system). Planning a few upgrades and mods of my own during this project with a goal of 600 at the crank and maybe a little more if we push it. It is looking like at least 3 months to assemble all of the bits needed.

At least I will have lots of spares for my '79 Euro CIS car. Only a couple of things left to do on that one and the CIS should be fine as it is a mild build.

Mr Beau · 02-05-2022, 05:39 PM

Might want to consider Emtron. I've run across lots of people with AEM complaining about sync errors and other bugs.

T77911S · 02-07-2022, 10:56 AM

why no vacuum valve on dist.?

if your timing is not retarding under boost THAT is where your detonation and lean mix is coming from

gumba · 02-07-2022, 04:11 PM

What a fun project on my ex DP935. RSR RAcer has been keeping me up to date on the project. A serious horsepower and torque increase (approximately 600 ) via EFI, swapping out the K27 for a Garrett,TK fuel rails and injector blocks,and a few other mod. Wish I lived closer this would be a brutal ride.

krasuskyp · 02-07-2022, 05:14 PM

if you're leaning out @ 4500 you've another issue beyond general 930 CIS limitation

5500 is the predominant cliff drop, with few / far between exceptions (every blue moon one arises)

I'd toss CIS in a heartbeat, but not for your reason alone

mikedsilva · 02-10-2022, 01:20 PM

Quote:

Originally Posted by Mr Beau

Might want to consider Emtron. I've run across lots of people with AEM complaining about sync errors and other bugs.

As one of the people who experienced the sync errors, I found that it ended up being where the cam sync was in relation to the crank trigger. I don't claim to fully understand it, but using an oscilloscope was able to determine where the cam trigger was in relation to crank, and simply reclocked the cam pickup to suit.

Some of the other ECU software have a built in oscillosope... motec, Ecumaster..... but the AEM does not. If AEM were able to incorporate this, I bet there would be fewer issues reported.

dos531 · dos531's Garage

Do it! Getting rid of the CIS garbage was the best thing I ever did to my 930. Message me if you need any help.

T77911S · 02-11-2022, 03:14 AM

I was thinking about you the other day while driving.
you have twin plugs and 26 degrees advance and no vacuum pot.

THATS your problem.
you don't need that much advance with twin plug. that's your detonation plus your taking HP off the table.
the earlier the fuel is ignited the more it pushes down on the piston as it is still trying to rise.

advance should be set on a dyno. increasing timing until no gain in HP. anything beyond that is reducing HP.

Mr Beau · 02-11-2022, 07:43 AM

Quote:

Originally Posted by T77911S

advance should be set on a dyno. increasing timing until no gain in HP. anything beyond that is reducing HP.

It won't knock before HP stops gaining?

gumba · 02-11-2022, 09:36 AM

Not sure why the CIS discussion is continuing since the OP stated he was switching to EFI for a significant HP gain.
T 77 911S; Jerry Woods built and dynoed the motor and ultimately decided the advance. You would need to talk to Andial about the lack of a vacuum valve on their 12 plug distributor.

RSR Racer · 02-11-2022, 11:03 AM

Gumba is correct. The DP is moving to EFI. I will leave the CIS on my other '79 930 (although its nearly at the limit of the CIS now) but I really want to do more for the DP.

Currently am collecting bits and working out the details to go with Motec. I have AEM on another one and it runs great but am still tinkering with the tune to smooth out some rough spots. The flexibility offered with Motec is crazy - even did knock control on the race car and it works great!

I really appreciate the thoughts on the CIS. I still need to get better with that system as I intend to really try and limit what I do to that one. Some of the cool bits from the DP will likely end up on that car. Planning an intake mod this spring and then that should be it......at least until the DP and one other project is done. LOL

mikedsilva · 02-11-2022, 08:48 PM

Quote:

Originally Posted by RSR Racer

Gumba is correct. The DP is moving to EFI. I will leave the CIS on my other '79 930 (although its nearly at the limit of the CIS now) but I really want to do more for the DP.

Currently am collecting bits and working out the details to go with Motec. I have AEM on another one and it runs great but am still tinkering with the tune to smooth out some rough spots. The flexibility offered with Motec is crazy - even did knock control on the race car and it works great!

I really appreciate the thoughts on the CIS. I still need to get better with that system as I intend to really try and limit what I do to that one. Some of the cool bits from the DP will likely end up on that car. Planning an intake mod this spring and then that should be it......at least until the DP and one other project is done. LOL

Interesting comment about the motec.. The AEM also has knock control doesn't it?
What does Motec offer above the AEM? Does the software make a difference to how an engine performs? Genuine questions...

porsche 930twin · 02-13-2022, 12:20 PM

Another very important advantage with Motec is its Australian made...

T77911S · 02-14-2022, 03:49 AM

Quote:

Originally Posted by gumba

Not sure why the CIS discussion is continuing since the OP stated he was switching to EFI for a significant HP gain.
T 77 911S; Jerry Woods built and dynoed the motor and ultimately decided the advance. You would need to talk to Andial about the lack of a vacuum valve on their 12 plug distributor.

personally I like to why something is not working right.

also, perhaps a simple change in timing can get him driving until he gets the parts for EFI. I would back the advance back to around 18 just to see what it does.

I would assume the twin plug dist does not need the retard pot since it is twin plugged. maybe someone that is twin plugged can add something.

RSR Racer · 02-14-2022, 08:29 AM

Quote:

Originally Posted by mikedsilva

Interesting comment about the motec.. The AEM also has knock control doesn't it?
What does Motec offer above the AEM? Does the software make a difference to how an engine performs? Genuine questions...

The AEM system I have is older and does not do knock control. I know the latest generation AEM ECUs do - at least their top of the line one does. I like the AEM, but have a close friend that also happens to be a Motec dealer and has tons of experience tuning these systems. We will put the engine on his dyno and spend a few days getting it right - and his shop is 15 minutes from my house.....

RSR Racer · 02-14-2022, 08:34 AM

"Another very important advantage with Motec is its Australian made... "

So true - Which makes it sooooooo much easier to get here in the USA with all of the supply chain issues! LOLOL

RSR Racer · 02-14-2022, 08:44 AM

The car actually runs really well. Just can't plant the throttle and hang on to redline. I watch the AFR and make sure I'm off it before it gets too lean. Since it is going to take a few months to collect everything, I'll have it out and about, once the roads are in reasonable shape again, until we are ready to pull the engine. It's too much fun to leave in the garage!