930 efi power sorting
 

I want to list my mods then my problems in order to ask for help in safely raising my power level to what it should/could be.

Engine is Carrera/930 block from 84' Not split so original rods and rod bolts.
Cylinders are turbo 3.3 and pistons je forged 8.1/1. Fresh top-end with fresh Carrera heads.
ARP head studs I believe....
cams are Carrera currently.
Using Carrera intake and fueling rails but with built intercooler and 82lb injectors.
Turbo in Garret gt35r and fresh/good.
Headers are B&B with heat. Wastegate location is moved straight back but the outlet unchanged and not upgraded in my opinion just esthetically different.
I am using a 1 bar spring and that is working.
I have a custom exhaust with flow through muffler and an after 200cell cat. My system is valved but I have not opened the valve yet or on the dyno.
I am running electromotive tec200gt which is good. I can adjust whatever I need and it makes those adjustments. (I say this because I don't want people to get hung up on that unit as the source for my problems, I realize it's limitations but I'm not getting hung up from this unit yet.)
I have coil on plug and fresh plugs currently.
I have no boost leaks.
I'm running a short 930 trans no real complaints I guess.
934 clutch pressure plate and disk.

I did dyno this and with the 14psi I got a dismal 320hp on a dynojet.
I expected more but I did expect less than it should be as I do have a couple issues to sort out.

Issues:
Using a infrared thermometer I get 150-225* difference in temp of the headers from one bank to the other. my right side seems to have a different fuel pressure or some other reason for this variation.
Example 500f on left side and 325f on right idling. I'm not a mechanic though I can assemble one of these engines (I did not build this one) but I don't know what effects things like cam timing might do to cause this type of problem or what other thing might have this symptom.
My brain keeps coming back to timing of the cam one side to the next but I don't have reason for this thought.
The plugs were getting fouled with fuel before more tuning and it was always the right side bank and never the left......Something to think about.
Engine runs pretty well, I need to fine tune the tip-in and cold start a bit but otherwise it's smooth and nice.
I feel if I could sort this temp/fuel issue I could start raising boost and doing other things to get the moist of this engine combo.
My afr is safe on boost but the reference is after the muffler and a sampling of all sides obviously. My egt gets a bit hot on power but not alarmingly so. This is also sampling both sides. It does spike up to 1700f in extreme acceleration and goes right back down under normal driving to 1300-1450f at 75mph. Still I feel it's a bit hot.
I want to test my injectors they are new but i could swap them side to side...

What do you (those who have more knowledge than me) think about this?
Stephan Kasper? Chris Carrol?
Ideas?


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http://forums.pelicanparts.com/uploa...1736783265.jpg
http://forums.pelicanparts.com/uploa...1736783265.jpg
http://forums.pelicanparts.com/uploa...1736783265.jpg

Sorry I don't have any helpful advice but just wanted to say beautiful car you did a great job with it.

Thank you

Well it sounds like you already know one bank is running richer than the other. One thing to check would be the voltage to the injectors on each bank. If they're different voltages, the difference in latency could be enough to throw the fueling off significantly at idle.

I had a similar issue when I first built my 930 EFI engine. I checked everything to avoid rechecking the cam timing... it was the cam timing that was off left to right.

Agree with two things- very nice looking automobile and your cam timing is suspect. You’ve done enough troubleshooting and like David, you’re down to that. It’s doable in the car but depending on your shop situation it might be easier in the long run to drop it and do it on the floor.
What I would like to know from a Chris C is: what is the target exhaust temp? IOWs, one of the cams is different than the other, but which is “better”? Don’t assume the colder one is. Camgrinder gave me a range to set my SC grind cams when I assembled my engine during Covid… I don’t think there’s a wrong answer in the range per se but they should both be set equal to the other.

Definitely think they should be set the same.

As far as to where they should be set in the range, I had my SC cams set "retarded" (eg timed towards the late-opening end of spec) way back when (2006?). Someone said at one time that this would help reduce blow-through due to timing overlap under boost and help spool.

For a subsequent round of work a year or two later, shop (different one) said they set the cams to "more normal" timing figures - and that they thought I'd much prefer it.

They were right; drove considerably better better off-boost (better yet with extra advance), much more responsive. No power loss noticeable on-boost.

For my money, time the cams as advanced as you can get within spec on both sides.

Nice-looking build!

A few questions, please:

Where are you measuring EGTs?
And are you using them as an input to the ECU?

Finally, are you running closed-loop, or open?

My engine was built by a good guy and I believe he knew what he was doing. The cam timing portion of the build is pretty hard to get numbers wrong as it's an obvious attempt to time if I remember but this thought has kept me guessing.
My efi doesn't use egt as a reference. I take the temp reading from the bung area under and before the turbo.
I believe the operation for the most part is open loop but I am not expert or up to the know on that..... Thanks for all the input.
Engine has about 6000miles if that. I have great leak downs and unsure on compression as I think my compression tester is dumb. Car runs smooth.

I guess I should say the 320hp is through a cat......will a cat remove 50hp?!

I would figure out what is causing this before worrying about power output:

Using a infrared thermometer I get 150-225* difference in temp of the headers from one bank to the other.

If one bank is running lean, then you could cause major engine damage.

Try taking the temperature of each stub pipe at idle at the same distance to the exhaust port and see if maybe one cylinder is not firing at idle?

I've had pins back out on the COP plugs when changing plugs and cause a cylinder to not fire all the time.

John

Typically EGTs are taken within a very short distance of the exhaust valve. I would say 4" would be the max distance, often shorter. The exhaust has a long time to cool before it gets to where you're measuring it if I understand your description.

True

With info provided, I'd guess that you're on the right path suspecting a fuel pressure delta between banks.

Asking the dumb question: Are all the injectors the same, and are they all firing the same (no tunings applied in the ECU)?
Not as dumb questions: How is your fuel system plumbed? - have a diagram that's sharable?
Using a return system, or dead-headed? Are the banks in serial or parallel? Where's the fuel pressure regulator? Are you using 90° fittings (not radiused)?

What I'm getting at - there's a lot of ways you can have different fuel pressure at different banks and it might be worth investigating.

???
I had an extensive reply written out but it didn't post after all.
Give us a call, way faster than re-typing.

When you say one side plugs fouled and the other not, is the plug color noticeably different? Mine were drastically different like white plugs on one bank and dark brown on the other bank.

One of my plugs was still stuck

I had a cam timing issue that I thing was caused by an accident.
My no1 side was timed 1.9mm at z and no 4 side was showing .16mm at z so I assume it was off by maybe a tooth or two I don't know but it was off for sure.
So....it's all back together same setup other than a new flywheel that is a couple lbs heavier which helps on the commute lol.
I have basically had to retune it. This is where I falter. My "new tune" that I thought I was so crafty and smart to do was as mess when I drove it, 10 afr or worse on cruise. So I reverted back to an older known tune but for an engine that was not right look above for why. It does run better and sounds much smoother. I'm happy but since I pulled a lot of timing out because I read and hear that 30-35 degrees is a lot I don't want to damage the engine but it's just not making the power. Probably less than 300 or so. I guess I can keep messing with it but I don't have knock sensors yet and im old and deff. Any pointers? I'd like to see more ignition maps and stuff so I can compare and make adjustments.

Here is my base ignition map - nothing much changes from 4K+ in my map
I do some other minor compensations for high intake air temp, high engine temp, and cold engine temp. Engine is designed to run on super unleaded with a max boost of 0.9 bar.

The timing hole just above idle helps keep things smooth and consistent with or without the AC running.

I found having an advance in the mid 30's helped significantly under low load "cruise" conditions. My target AFR is ~0.97-0.98 steady state cruise and 0.8 at full boost.

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