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CIS + Big turbo = too lean. Advice for more fuel?

I need to get more fuel @ WOT in my CIS 964T.

Chris from Turbokraft has been extremely helpful in supplying go-fast bits and lots of associated set-up advice but I have reached a dead-end trying to get more fuel. Here are the pertinent details.

1992 964 turbo
-Fresh 3.3L build with JE 8:1 pistons, Supertech studs, 36mm intake ports, SC cams, upgraded springs w/Ti retainers, etc
-GT35RS turbo w/4" compressor housing
-Fabspeed headers & 3" TK exhaust (no cat)
-Rebuilt CIS Flowtech US-spec fuel head, Bosch 044 pump in rear location, new injectors & Leask WUR + RPM solenoid kit
-TiAL WG with MBC

At WOT the AFRs are great (in the 11s) all the way until 6000rpm. From 6000 to 7000rpm the AFRs slowly climb from the upper 11s into the 12s.
At 0.7bar I see a peak of 12.2 AFR between 6500-7000rpm
At 1.0bar I see a peak of 12.8 AFR between 6500-7000rpm

The WUR is adjusted to the following settings:
Cold Control Pressure 3.1bar
Warm Control Pressure 4.5bar
Enrichment Pressure .... started at 2.9bar, then adjusted down to 2.6bar and now at 2.45bar. This helped a bit but still isn't enough. Can I go lower?

My goal is for the AFR to never go leaner that high 11s, i.e. I don't want to see the number 12 on my Innovate gauge! The car spends most of it's life drinking 94 octane w/10% ethanol.

Any thoughts as to why I can't get enough fuel beyond 6000rpm? I know guys have made more power with CIS cars than I am making. The GT35RS isn't that big so I have a hard time believing that the upgraded/modified CIS system is beyond capacity.

I am open to suggestions
Old 06-30-2011, 10:36 PM
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I don't think any of the guys are making much more power than you over 6000rpms. There just is a limit of how much we can get out of CIS. The fuel head can be opened up if it already isn't and you can alway install water meth injection with failsafe.

You could boost up your midrange up to 6000rpms if your heads can take it. HW vise you seem to be pretty much done if the IC is big. How about backpressure? You could also try a bit bigger hotside.

Thierry and sti have seen that controlling the WUR line with ie. split sec AIC1 should give some more fuel too.

Not an expert but on the same CIS boat and I'd like to stay that way too.

Last edited by smurfbus; 07-01-2011 at 12:02 AM..
Old 07-01-2011, 12:00 AM
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Nice and interesting setup

If my understanding is correct, you are using SC cams right ?

I would be curious to see your torque curve. But, just my 2 cents experience, there is already (too) much enough fuel on the top end RPM. (between 6000 and 7000). There is absolutely no detonation in this RPM range.

The SC cams doesn't allow to get huge filling at such high RPM ( I bet the TQ peak occur near 4600 rpm). Below 12.5 (assuming your injectors are flow matched) , the more fuel you will add on AFR , the higher temp you will get on EGT !


That having been said, if you still want to get more fuel , the first thing to do is to install a 044 fuel pomp in front. The second thing is to install the flow matched 3.6T injectors . ( if you kept the lambda function, there is no problem with idle and low RPM )
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Old 07-01-2011, 01:34 AM
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You say the fuel head is rebuilt, has it been modified to flow more fuel than stock?
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Old 07-01-2011, 04:18 AM
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What is your system pressure?
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Old 07-01-2011, 04:18 AM
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Quote:
Originally Posted by smurfbus View Post

You could boost up your midrange up to 6000rpms if your heads can take it.
I have a similar opinion...

Actually, with these cams ( whatever they are timed), there is no need to " rev the moon " ( I learn this funny word from Chris )

Beyound ( let's say) 5000 rpm, these cams are something like out of breath. ( At least they need huge boost pressure with too huge expense on the back pressure side ...).

With this setup, I think there is no problem to extend the boost level to 1.2b (even more/ depending the fuel octane) in the lower range 3000 -5500. Then beyound this rpm, it's better to lower it progressively and to do not over 1b above 6000 rpm.
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Old 07-01-2011, 04:41 AM
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What is your system pressure?
That's a good question .

I bet he already shimmed the pressure regulator and get something like 7.5 bar under static measurement.


But this is fuel system pressure at rest......
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Old 07-01-2011, 04:51 AM
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What is your WHP?
I would expect ~400WHP and if that is correct you should be able to adjust out your lean spot up top. A touch more system pressure, a touch more flow out of the head, it shouldn't take much.
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Old 07-01-2011, 06:03 AM
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Thanks for all of the replies. Lots of great info!

I am ashamed to report that I don't know what the CIS System Pressure is set to. Is this pressure easy to adjust (increase)? What pressure is ideal for a set-up like mine?

The engine does have SC-spec cams, timed to approx 1.6mm IIRC.

I have yet to dyno the car but my semi-accurate butt dyno says that it continues to pull hard and make power to at least 6500rpm. I agree that the torque peaks feels to be in the mid-4000 range.

Thierry25, I am willing to install another 044 pump up front and 3.6 injectors if you think it will make a measurable difference to the top-end fueling. FWIW, I know of some 500hp turbo 911s running single pumps, but these are EFI cars so maybe it isn't fair to compare?

The fuel head was rebuilt by Larry @ CIS Flowtech and at the time I asked him to modify it for a "bit more" output. I haven't been able to confirm exactly what he did, modification-wise, but I don't think he went all-out like he did for some of the IA fuel heads. The Lambda control is still active and pulls out plenty of fuel at ideal and cruise. Actually, at light-load, low-RPM cruise the cycling of the O2 in the 14.4 - 15.2 range causes a very slight surge so the car drives better with the O2 unplugged and the AFR steady around 14.

Does anyone think that an AFR of ~12.5 past 6000rpm @ 1bar isn't too lean?
Old 07-01-2011, 07:22 AM
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"Enrichment Pressure .... started at 2.9bar, then adjusted down to 2.6bar and now at 2.45bar. This helped a bit but still isn't enough. Can I go lower?"

Yes it can go lower. Use the tool supplied by Brian Leask with the adjustable WUR to pull out the disc on the bottom to lower boost control pressure more.
Thread the 4mm stainless allen head stud in the middle of the tool into the disc and try turning the 10mm nut on the tool clockwise 1/4 turn at a time to pull the disc out lowering internal spring tension and boost control pressure. Then slide it back on the studs and road test to see the results on your AFR gauge. You can always press the disc back in with a C clamp or completely remove the WUR and tap it back in with a brass drift if you pull it out too far.

As you draw the disc out to raise boost AFR from where it is now you'll also see steady cruise AFR richening up a little bit with each adjustment so you'll probably want to turn the allen head in the midle of the disc clockwise about 1/8 turn at a time to compensate and lean the steady cruise AFR back to where you want it

It's relatively easy to readjust it this way and road test it and you don't need a laptop computer, just a calibrated wideband AFR gauge.

Doing it this way without removing the WUR for adjustments every time and watching your AFR gauge for the results is easier if a small air cleaner is installed to give you more room to reach it. With the stock air cleaner you'll have to remove the 2 bolts on top and the nut on the bottom, then lift it up an inch or 2 and push it back a couple inches and stuff a large rag under it where you can to hold it there to gain acces to the WUR.
Access to the WUR you gain doing that with the origonal air cleaner will be a little different with each car but I can do it on my car with a large Kokeln halfbay intercooler and foam rubber engine compartment sound pad in place.

I never bother to put the control pressure gauge on for this kind of WUR tuning so I don't know what the CP's are, I go by making visual 1/8 or 1/4 turn adjustments in steps to the WUR and watch the innovate MTX digital AFR gauge readings during road tests and readjust untill I like them.

You can stop in parking lots or side of a quiet road and unplug the 12 volt plug from the WUR, slide it up off the 2 mounting studs with the fuel lines and boost enrichment vacuum line attached (if it's long enough), turn it sideways in your hand and use the tool Brian Leask supplied to pull the boost control pressure adjustment disc outwards, a 3mm allen head to adjust the 3 boost threshold adjustment allen heads, and a 4mm allen head to adjust the warm steady cruise control pressure allen head in the middle of the disc.

If you're stock front fuel pump is good then I don't think you need to replace it with another 044 pump. It may help though I havn't tried it.
If an 044 fuel pump is noisier than the stock one maybe you can put something rubber around it to absorb some of the buzzing noise. I think some CIS Mercedes sedans did that and fuel flow through the pump motor cools it.
I'm not sure how much air cooling to the aluminum housing of the fuel pump is going on..

edit: You posted more information while I wrote the above... I never heard of Larry at CIS Flowtech leaving the lambda valve installed when he modifieds the fuel head for more flow.
He modified mine for 20% more fuel flow and the lambda valve is removed and fitting plugged among other things he does to it.
You should call him and ask what he did to yours and if you can adjust it enough to get it where you want. You can also send it back to him and he can adjust it for more fuel flow without messing up low speed drivability from your description.
Did he stamp "007" on the back side where the origonal bosch part number tag was riveted on? He usually does that on his modified aluminum lambda fuel heads.

Last edited by JFairman; 07-01-2011 at 03:36 PM..
Old 07-01-2011, 07:26 AM
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Quote:
Originally Posted by JFairman View Post
"Enrichment Pressure .... started at 2.9bar, then adjusted down to 2.6bar and now at 2.45bar. This helped a bit but still isn't enough. Can I go lower?"

Yes it can go lower. Use the tool supplied by Brian Leask with the adjustable WUR to pull out the disc on the bottom to lower cold control pressure more.
Thread the 4mm stainless allen head stud in the middle of the tool into the disc and try turning the 10mm nut on the tool clockwise 1/4 turn at a time to pull the disc out lowering internal spring tension and boost control pressure. Then slide it back on the studs and road test to see the results on your AFR gauge. You can always press the disc back in with a C clamp or completely remove the WUR and tap it back in with a brass drift if you pull it out too far.

As you draw the disc out to raise boost AFR from where it is now you'll also see steady cruise AFR richening up a little bit with each adjustment so you'll probably want to turn the allen head in the midle of the disc clockwise about 1/8 turn at a time to compensate and lean the steady cruise AFR back to where you want it
Thanks for the reply. Is there a minimum no-no pressure that one shouldn't drop below? I.e. can I run the Enrichment Pressure down to 2.0bar? You called this Cold Control pressure....are we talking about the same adjustment?

I definitely need to remember to adjust the allen head in the middle of the disc so it doesn't get super rich at steady state cruise.
Old 07-01-2011, 07:34 AM
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"Thanks for the reply. Is there a minimum no-no pressure that one shouldn't drop below? I.e. can I run the Enrichment Pressure down to 2.0bar? You called this Cold Control pressure....are we talking about the same adjustment?"

I don't know if there is a minimum boost control pressure you can reach and don't want to go lower than. Seems there would be for it to remain drivable and normal in all situations.
Thats definately a question for Larry Fletcher, nobody else knows as much about that and CIS then he does.

I never mentioned cold control pressure adjustment. Thats a different catagory and I do use the CIS fuel pressure gauge and take ambient temperatures in relation to cold start control pressure I've written down previously into account when adjusting that.

I only mentioned the boost enrichment, boost threshold, and warm steady cruise control pressure adjustments on the bottom of the WUR so we are talking about the same adjustments.. I think.
Old 07-01-2011, 08:06 AM
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Quote:
Originally Posted by Ringmaster View Post
Thanks for all of the replies. Lots of great info!

I am ashamed to report that I don't know what the CIS System Pressure is set to. Is this pressure easy to adjust (increase)? What pressure is ideal for a set-up like mine?

The engine does have SC-spec cams, timed to approx 1.6mm IIRC.

I have yet to dyno the car but my semi-accurate butt dyno says that it continues to pull hard and make power to at least 6500rpm. I agree that the torque peaks feels to be in the mid-4000 range.

Thierry25, I am willing to install another 044 pump up front and 3.6 injectors if you think it will make a measurable difference to the top-end fueling. FWIW, I know of some 500hp turbo 911s running single pumps, but these are EFI cars so maybe it isn't fair to compare?

The fuel head was rebuilt by Larry @ CIS Flowtech and at the time I asked him to modify it for a "bit more" output. I haven't been able to confirm exactly what he did, modification-wise, but I don't think he went all-out like he did for some of the IA fuel heads. The Lambda control is still active and pulls out plenty of fuel at ideal and cruise. Actually, at light-load, low-RPM cruise the cycling of the O2 in the 14.4 - 15.2 range causes a very slight surge so the car drives better with the O2 unplugged and the AFR steady around 14.

Does anyone think that an AFR of ~12.5 past 6000rpm @ 1bar isn't too lean?

Yes you should check your "static" fuel pressure system first . If your pressure is still at the stock value ( around 6.8), you can increase it to 7.5- 7.9 by adding a simple washer into the fuel pressure regulator. It could bring you very few more fuel.... but not such important increase since the problem comes from the pumps flow capacity.

I spoke about "static" pressure because this is not the real dynamic pressure. Actually, when CIS metering arms is moved to it maximum position ( thus when the CIS deliver the max of fuel into the intake), the system pressure drop by about 1.5 bar ( this is what I measured even with my 044 in front )

Unlike the EFI system which can work correctly with 4.5 bar of system pressure, the CIS need higher pressure (min 6.8 bar) . At such higher pressure, the fuel pumps flow capacities are dropping a lot. Moreover, the lambda regulation as well as the WUR draw back some fuel to the tank. So that's why the CIS need better fuel pumps than EFI.

Yes, the front 044 will bring you more fuel.
Yes the 3.6T injectors will bring you more fuel ( 5% more ). I already compare both injectors capacity . Absolutely no doubt !

I am agree with your experience regarding the lambda regulation. (assuming you disconnected the O2 sensor and you kept the freq valve connected) . That's true that the AFR is oscillating between 14.2 to 14.7. The car drives better with no regulation and AFR arround 13. However this regulation may help you if you decide to install the 3.6T injectors.
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Old 07-01-2011, 08:14 AM
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Salut Thierry25

Quote:
Yes you should check your "static" fuel pressure system first . If your pressure is still at the stock value ( around 6.8), you can increase it to 7.5- 7.9 by adding a simple washer into the fuel pressure regulator. It could bring you very few more fuel.... but not such important increase since the problem comes from the pumps flow capacity.
I will check this right away. Where would I place this "washer" to increase the pressure?


Quote:
Unlike the EFI system which can work correctly with 4.5 bar of system pressure, the CIS need higher pressure (min 6.8 bar) . At such higher pressure, the fuel pumps flow capacities are dropping a lot. Moreover, the lambda regulation as well as the WUR draw back some fuel to the tank. So that's why the CIS need better fuel pumps than EFI.
Good to know.

Quote:
Yes, the front 044 will bring you more fuel.
Yes the 3.6T injectors will bring you more fuel ( 5% more ). I already compare both injectors capacity . Absolutely no doubt !
I will check and adjust the static system pressure first. Next I will try lowering the Enrichment Pressure on the Leask WUR down closer to 2.0bar. If neither adjustment gives me enough fuel up top I will install the 3.6 injectors and front 044 pump.


Quote:
I am agree with your experience regarding the lambda regulation. (assuming you disconnected the O2 sensor and you kept the freq valve connected) . That's true that the AFR is oscillating between 14.2 to 14.7. The car drives better with no regulation and AFR arround 13.
The O2 sensor is new and the freq valve is still connected/active.


Thanks
Old 07-01-2011, 08:45 AM
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some great WUR insight there Jim / Thierry (can you please chime in to my AFR thread just below? I could use some similar insight for sure! Thanks!)

Great build btw, sounds like a neat car - good luck / enjoy!
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Old 07-01-2011, 08:54 AM
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Before you spend the money on another 044 fuel pump and the adaptors needed to install it check the voltage at the actual fuel pump wires under the car and see what it is in relation to the battery voltage.
There will be some voltage drop from all the wiring but the amount will vary car to car year to year and condition of the fuses, wiring, and relays.
Old 07-01-2011, 09:04 AM
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Quote:
Originally Posted by Ringmaster View Post
I need to get more fuel @ WOT in my CIS 964T.

Chris from Turbokraft has been extremely helpful in supplying go-fast bits and lots of associated set-up advice but I have reached a dead-end trying to get more fuel. Here are the pertinent details.

1992 964 turbo
-Fresh 3.3L build with JE 8:1 pistons, Supertech studs, 36mm intake ports, SC cams, upgraded springs w/Ti retainers, etc
-GT35RS turbo w/4" compressor housing
-Fabspeed headers & 3" TK exhaust (no cat)
-Rebuilt CIS Flowtech US-spec fuel head, Bosch 044 pump in rear location, new injectors & Leask WUR + RPM solenoid kit
-TiAL WG with MBC

At WOT the AFRs are great (in the 11s) all the way until 6000rpm. From 6000 to 7000rpm the AFRs slowly climb from the upper 11s into the 12s.
At 0.7bar I see a peak of 12.2 AFR between 6500-7000rpm
At 1.0bar I see a peak of 12.8 AFR between 6500-7000rpm

The WUR is adjusted to the following settings:
Cold Control Pressure 3.1bar
Warm Control Pressure 4.5bar
Enrichment Pressure .... started at 2.9bar, then adjusted down to 2.6bar and now at 2.45bar. This helped a bit but still isn't enough. Can I go lower?

My goal is for the AFR to never go leaner that high 11s, i.e. I don't want to see the number 12 on my Innovate gauge! The car spends most of it's life drinking 94 octane w/10% ethanol.

Any thoughts as to why I can't get enough fuel beyond 6000rpm? I know guys have made more power with CIS cars than I am making. The GT35RS isn't that big so I have a hard time believing that the upgraded/modified CIS system is beyond capacity.

I am open to suggestions



Try straight gas, it takes 2 1/2 time as much ethanol to equal the BTU's put out by gas
Old 07-01-2011, 09:16 AM
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You don't need to spend any money on new parts if the ones you have a working.
If your engine is putting out ~400WHP as suspected you can simply tune in the fuel needed as Jim described. Dropping from 12.5 to 12.2 or so should be do-able.
I'd sure try that first.
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Old 07-01-2011, 09:38 AM
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Quote:
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Salut Thierry25


I will check and adjust the static system pressure first. Next I will try lowering the Enrichment Pressure on the Leask WUR down closer to 2.0bar. If neither adjustment gives me enough fuel up top I will install the 3.6 injectors and front 044 pump.

Thanks
Hey .... you speak french ???

Yes you can lower the PC to 2.0 b. There is no basic problem to reach this PC. However you will certainly get more fat mid and you will increase the PC recovery time. ( if PC is too low , the transient response during gear shifting and throttle off response are affected ). Past a certain value, you can lower PC to whatever value.......... you don't get any additionnal fuel on very top end. ( You can even get a little less since the WUR catch a little more fuel flow )
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Old 07-01-2011, 10:13 AM
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If you have a gauge to check system pressure at the WUR, (I guess you do if you're going to experiment with the tiny washer like shims under the main spring in the fuel heads tiny system fuel pressure regulator) the compression fitting in the line from the front fuel pump where it screws into the inlet of the rear fuel pump is the same size as the control pressure feed line on the WUR.
You can buy a CIS fuel head pressure regulator rebuild kit here from pelican for about $50 and I think it has some shims in it along with the orings and springs, or take one out and try to match it up somewhere, or call Larry and see if maybe he'll sell you some.
They are thin and tiny and sometimes there are 2-3 of them stacked together under the spring.

To check fuel pressure from the front pump remove the compression fitting and line going into the rear pump and screw it into the CIS pressure gauge and flip the ball valve lever 90degrees to the line so it blocks flow and reads system pressure. Turn on the front pump while the rear fuel pump relay is removed so the rear one isn't running dry and the gauge will show what the mazimum pressure available from the front pump is. I don't know what that spec should be.

With the other end of the CIS pressure gauge line screwed into the inlet of the rear pump at the same time and the ball valve open so fuel flows through the lines you can check the pressure from the front pump while everything is hooked up and both pumps are running including with the motor running fwiw.

There is a small pressure relief valve in all high pressure Bosch rotory roller fuel pumps and it opens and recirculates fuel inside the pump when flow from the pump is blocked or close to it so the pump doesn't labor, overheat, and burn out trying to run.
I never knew it was there until I took apart a seized bosch fuel pump from a BMW years ago and saw it there. It's a little spring loaded ball valve in between the the pressure side after the rollers and the electric motor armature side of the pump before the rollers.

I also did not know the entire electric motor, it's bearings, it's commutator and brushes are all in the gas flow with gasoline flowing around them. The gas flow cools and lubricates the motor and doesn't explode in flames from electrical sparks at the brush to commutator contacts because there is no air in there.

Totally agree with Brians opinion on spending $1000 on another 044 pump, the fittings to install it, and six 3.6 CIS fuel injectors to get a little more fuel at 6500rpms

I'd sell all the CIS crap you have and do megasquirt 3 EFI before doing all that to get .5 richer AFR at 6500rpm..
The much increased throttle reponse of EFI with no mechanical air flow meter working against fuel system pressure to open and get out of the way of the intake air flow would be worth that alone if you're up for the adventure...
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