Crappy Dyno Run (Part Deux)
 

I'm transitioning my "Crappy Dyno" thread to Technical because it does not really involve Engine rebuilding anymore. See link for background:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/802486-crappy-dyno-results-3-4l-rebuild.html

The summary is: Poor power after 3.2 to 3.4 rebuild. Problem seems in to be in Motronic.

Clarification on engine configuration: By matched injectors I mean that they are OEM, but checked to ensure they are equal. I'm currently running the AFM (flapper). I took the MAF (hotwire) off to see if that was the problem. Also, the wideband O2 is on left hand side, so I have no idea of the right cylinder bank AFR (I have headers). I have a new fuel pump and fuel filter.

Dead cylinder? I think that is VERY possible and I planned on checking that this weekend, but I did not get that far.

High fuel pressure: Yes I agree that is not a good solution. I plan on setting the Motronic up exactly via Bentley and doing every test.

What did I do this weekend? having trouble prioritizing what to check, I started at the gas pedal and moved back.
• Throttle linkage adjustment: I set the linkage under the transmission. I checked the throttle body butterfly valve for correct positon when idle and pedal full down--both checked good.
• Idle switch—it failed. Resistance did not change with throttle movement and RPMs did not change when disconnected.
• Checked for vacuum leaks with carb cleaner—I couldn’t find any…. but, I opened the oil filler and got no RPMs change--Indicating a leak, but it might also be caused by the bad idle switch? Not sure; so, I called it quits.
What’s next?
• New idle switch will be here in 10 days (out of stock). While I am waiting, I can disconnect (electrically) the ICV completely (switch and valve) and continue checking. Right?
• I will retest for vacumm leaks. My engine gets leaner at high RPMs, where there is more suction, so I think it is likely leaking. I’ll test with ether this time.
• Test for dead cylinders will be quick and easy. I’ll also pull the spark plugs and look for rich/lean conditions.
• Set fuel pressure
• New DME relay (I got a spare)
• Check ignition timing and advance
• Check for bad ECU (DME)
• Check electrical system voltage
• Check altitude switch
• Cylinder temp sensor
• Gas tank breathing/venting

Oh boy

I have no help for you other than take lots of notes and make your changes in a stepped manner starting with the simple stuff. Get that vacuum cleaner and tennis ball out to trace those vacuum leaks.

Hmmm. I seem to recall the idle switch had 2 functions:

1.) Tell the DME throttle was closed, and to take over idle functions using the ICV.
2.) Tell the DME when you opened the throttle, stop modulating the ICV, AND advance the timing!

There is also a WOT sensor. I recall the DME uses the idle and WOT sensor to alter the timing and fuel injection

Your injectors are too small. The stock ones are too small for a
3.2 then add .2l and 15% alcohol and your really too small

I found a couple vacuum leaks tonight (see pict). Boy, I have new respect for vacuum lines. I went thru and tightened every hose clamp I could find. I probably won't have a chance to fix the cracked hoses until the weekend. Also, the Idle switch will take 10 days to get here.:( So, no update on drivability.

(I also checked and cleaned the ICV.)

Injectors too small? Yes, some others have already suggested this. For now, I am going to fix the below 4,000 RPMs... but to get the most out of the higher RPMs, I may be looking at bigger injectors and a new SW chip.

http://i1349.photobucket.com/albums/...ps360f2d1f.jpg

We are working on a 3.4 build, what size injectors should be be looking at????

Did not get much done this weekend, but here is what I did:

• New fuel pressure regulator (difficult to get back there)
• Repaired vacuum leaks
• Checked static timing (good)
• New DME Relay
• Checked for dead cylinders (none)

Then I did a couple runs with my LC-2, here is what I got:

<a href="http://s1349.photobucket.com/user/tpjung92ungspike/media/LM_2_data_zps858f281b.jpg.html" target="_blank"><img src="http://i1349.photobucket.com/albums/p759/tpjung92ungspike/LM_2_data_zps858f281b.jpg" border="0" alt=" photo LM_2_data_zps858f281b.jpg"/></a>

(Yes, I know this sucks). Next step is to swap out the DME and chip. Hopefully chip was designed for higher octane, non-ethonal gas. (I am still waiting for new Idle switch).

Oh boy, running out of ideas...
Tim

This is what is still on my list (prioritized list):

1. Swap DME
2. install idle switch
3. Set base idle
4. Replace rotor and cap
5. Replace flapper box for hotwire MAF sensor
6. Check ignition advance
7. Check fuel pressure
8. Look for more vacuum leaks (2nd time)
9. Pull the plugs and look for rich/lean
10. Check altitude switch
11. Check cyl temp sensor
12. Check electrical system voltage check
13. Confirm gas tank breathing
14. Dead cylinder (2nd time)

After #14, I'll start looking into bigger injectors. No one ever answered JcSlocum's question about good injectors for a 3.4 rebuild (I didn't answer cause I ain't no expert, but I estimate that you need injectors capable of 24 lbs/hr to support 240 BHP. I'm not sure what part number people use to get this flow rate, I guess Stan Weiss's web page is the place to start shopping:

http://users.erols.com/srweiss/tableifc.htm#BOSCH

You have huge cams in there and stepped up displacement. You simply need a custom chip burned on a dyno through Wong IMO.

You're gonna pick up big power once those AFR's get back into the 12's.

Your DME is fine I'm sure. And yes, the WOT switch is super critical. A continuity test is all that's needed to see if it works. It's normally open until WOT, then your multimeter should "beep".

Jung,

FWI if those are full power full load passes I would back off sooner than later or you will be doing all this again. Full load at 13.5 AF stops us on the dyno cold at 15.0 AF we pull it or find the issue as it will eat parts that lean.

If adding fuel pressure is not an option with this EFI you will need to find another solution. Ignition advance / detonation does not show up as a dead lean condition IMHO.

Please get some help getting the AF in check before this goes south.

If you run with the stock air flow meter, make sure you are using a chip program designed to run with the stock air flow meter, and not one for the Autothority MAF. If using the Autothority MAF, you need a special custom chip for that sensor. The two are completely incompatible as the V(out) curves are a complete inverse of each other. I don't see what chip and sensor you're using in your AFR test, but from its looks I'm guessing you're doing a mix and match.

Yes Steve you are correct. I'm a dumby. I was running a chip meant for the hotwire MAF with the stock flapper box.

I put the MAF back on and it runs MUCH better.

However, AFR still climbing to 15.0 at 5,000 RPMs.

I'm done for tonight, but I am excited for the improvements... Thanks Steve!

Then you need to decide whether you're going to use the stock AFM or the Autothority MAF and have a custom chip programmed to match. There's no other way around it. You purchased a parts package with a program someone else used in his engine, and just cannot build your custom motor out of it and expect the tune to be the same. Engine builds just have too much variation in assembly and components from one to another.

A good running 3.4 running on pump gas and with some cams should dyno at least 230 RWHP SAE on a Dynojet. The underperforming ones dyno 220 or less, and that has been usually attributed to a restrictive exhaust such as SSIs. In fact the stock exhaust including the stock muffler performs much better and those are the ones that have no trouble hitting 230-235.

If a 3.4 dynos at 200, that's usually either because the cams are improper or severely mistimed, or possibly the pistons are not meeting compression, along with a restrictive exhaust.

Installed the flapper box and a borrowed chip (chip maker is Road & Race Inc.) and did a run. Here is what I got:
[IMG]http://i1349.photobucket.com/albums/...ps215aa179.jpg[/IMG]
The "dyno" data was on a Dynojet (with Hotwire), the "Hotwire" data is from two days ago with the Autothority MAF and the "Flapper Box" is with the stock air flow sensor and the "Road and Race" chip. The last two sets of data are taken from my LC-2 wideband O2 sensor (I show the dyno data, only to show that the LC-2 matches it). So... I guess most of my lean problem is from from a chip that wasn't tuned for my engine (just like Steve W told me).

Yes, you have to get that car on a dyno and have a tuner like Steve W tune a custom chip.

Put some 46mm Pmo carbs on it and it will save the headache and make more power with cams:)

EFI is pretty much once and done. Doesn't seem so much with carbs. :)

Hi
Great that you fixed a few bits but clearly a custom remap is the only way forward.
Db

New SW chip is ordered. Unfortunately, I don't live close enough to meet SW at a dyno.

YermanCars, This experience has certainly made me understand why people like carbs, but I'll stick with the Motronic... for now.

Just got a new SW chip... Great improvement: AFR is now around 13.0 at all RPMs below 5k. (I won't take it above 5k till rings are seated.) I still have some parts of the Motronic that need to be checked/tuned. After I have gone through every part of the system and have 1,000 miles I'll re-dyno and report the results.

I appreciate all the help/advice from my fellow Pelicans.
Thanks,
Tim