ECU Problem at High Boost

[mgmshar]

I posted this on another Buick board, and got no response. Maybe somebody here can help me out...

Ever since I got my new turbo (TA-49) and Terry Houston DP, I've had a problem that I can't seem to lick. I imagine that somebody on this board has seen this before...

Whenever I run the car under high-boost conditions (i.e. 20+psi with the dump off the DP), the computer will shut-off the signal to the wastegate solenoid for a split-second at the top end of second gear or the bottom end of third gear. I know this is happening, because I can see it in the DirectScan data. At 5000+ rpm in second gear, the computer will drop the boost PW to zero, and then slowly bring it back up to the normal value. The result is that my boost drops from 20+ psi to about 15, and then slowly builds back up as I go into third gear. What's weird is that this happens every time with the dump off and high boost, but never happens when I run with the dump on and lower (i.e. 17psi) boost. On some occasions, I can see that the LV8 value and injector PW value also go to near zero at the same time as the boost PW. However, that doesn't always happen, unless the DirectScan isn't catching it.

I've tried several different chips of my own, and I've tried a Red Armstrong chip, and none of them seem to fix the problem. I've also tried several other things:

1. Replaced the MAF sensor.
2. Tightened the four grounds on the rear of the engine.
3. Checked both battery cables.
4. Jiggled/tightened the connectors to the ECU.
5. Put a Q-tip in the DirectScan cable connector to keep it from sliding too far onto the ECU board.

The problem seems to be in the ECU, because DirectScan is telling me that the ECU is dropping the boost solenoid PW to zero. The drop doesn't correlate with a knock event, a third gear transmission event, or anything else that I can see. Has anybody seen this before? Why would this only happen under high boost conditions, and always at the top end of second gear? Does this have something to do with the MAF reset problem that I've read about?

Any help would be GREATLY appreciated!

Amazingly, even with this problem, I managed to run my very first 11-second time this past weekend, on 100-octane gas. I'm still giddy about that one. It's amazing what 40 degree air will do for these cars!

Thanks,

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[Steve Y]

Out of curiosity, what is the voltage doing?
Reason I ask is that i suspect after a certain point the ecm will shut down the solenoid......not that this is happening in this case......just curios..
Steve

[Orlando_87GN]

From what you are describing, it sounds like some normal DS glitches. I have seen huge spikes in all the scales on occassion, especially when slowing down after a pass at the track.

Email your DS file to me, and I'll let you know if it's the same thing I usually see.

mailto:mike@jigawatt.commike@jigawatt.com</A>

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Stock Block, Stock Cam, PTE-52, Champion Heads, V4, MSD50's, TH DP, JayJackson 62mm TB, 16position MaxEffort Chip. 3750# with Driver
New E.T. Coming Soon.

mailto:mike@TurboBuicks.commike@TurboBuicks.com</A>

[TurboDave]

From what you're describing it sounds like you're suffering MAF buffer overflow. Very common in high boost high airflow scenarios.

The easiest cure without getting into the why's and wherefores of upgrading your MAF system, would be to get somebody to burn you a chip that has a MAF lock patch in it.

Because of the way certain events in the ECM are tied together, any droppouts in the MAF signal, will cause a corresponding drop in LV8, injector PW, and Boost PW.

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TurboDave & Kathy Huinker, mailto:TurboDave@turbobuicks.comTurboDave@turbobuicks.com</A>
TurboD Racing,Turbo Buick Web Ring
San Diego CA http://home.san.rr.com/buickv6/
86 GN11.80@116.9(MM/MAF Xlator/Extender,MM BstC Boost Command,THDP,PTE44,CAS V2FM,MSD50's,9.5"vigilante 3500)
87 GN 12.95@105.50(Stock)
84 Z28 L69
01 Excursion LTD TTS"race" chip 7.3L PSD(power stroke diesel) Turbo 4X2
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[mgmshar]

TurboDave,

What you are describing sounds right, and I've heard about it before. Problem is, I burn my own chips. I guess I would be willing to pay for one, if I knew that it would work.

Do you know who in the world burns chips with the MAF lock??? Otherwise, I'm going to have to really learn the Assmebler language (yuk!).

Mike

PS I have a PTE chip that's set-up for Red Stripes and 93-octane. Do you know if they have the MAF lock?

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[mgmshar]

A couple of other comments...

Steve, I looked at battery voltage during the boost solenoid drop-outs on one of my runs. I didn't see anything unusual. According to DirectScan, the battery voltage was around 13.8 volts, as I would expect.

Mike, I will send you a data file from one of my runs. Keep in mind that I can feel and see the boost dropping when one of these events happens. In other words, I think DS is recording something real.

I am inclined to agree with Dave that this is a MAF overflow problem, simply because it happens when I run at the track with high boost (20+ psi). When I run at "street boost" levels (~17psi), I never have a problem.

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[TurboBob]

It is definately MAF dropout.

It has all the symptoms.

The wastegate thing is due to the
software that enables the solenoid.
When the MAF value drops the wastegate
is disabled also and then has to ramp
back on.

A properly MAF locked chip will fix it.

The MAF translators have a limiter switch
which will fix this problem also.

TurboBob

[TurboJim]

I've also noticed that HD actuators exaggerate this condition. Like Bob says, probably MAf droputs

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Jim Testa
1986 Regal T-Type
Stock block w/girdle, stock rods, TRW's, JE pins, 214/210 roller, TurboMotion port/polished heads w/1.77-1.50 valves, T&D roller rockers, Champ intake w/o EGR, PTE plenum, Accufab 70mm TB, MSD50's, TE61, PTE front mount, SMC alcohol inj, JT trans, 3000 vigilante, stock rear w/Hotchkiss arms, and kick ass tunes..