excessive heat/ lose of power in 3rd

[jdmser]

Went to the track last night to get my new boost controller setup. I was able to accomplish my goal of getting the boost to hold at a solid 20psi. However, I have a new problem. It's launching fine and pulls hard in 1st and 2nd but, when I get into 3rd power drops off dramatically and by the end of the 1/4 mile my ect shoot from 180* to 210*. It also doesn't want to rev like it does in 1st and 2nd. It seem to get worse as the night went on. I had been running 18psi with no issue on my manual bleed valve. Any ideas? I actually lost about 5 mph off my trap speed.

[craz4240]

Is the car running lean at all?And what about timing?

[ANVIL]

did u try to back it off back to 18psi and see if it still did it? no funny noises or anything just lack of power?

what injectors/turbo are u using?

[jdmser]

It's a RB20 T3/TO4E 50 trim, Sard 720cc injectors, 11.5 ish ar, 15* timing, when shifting into 3rd the rpms would drop to around 4800-5000 and didn't want to go past 7k.

Never tried backing down to 18psi as it took all of my 5 runs to getting it adjusted to 20psi. Might try that tonight and see what happens.

[Darius]

What fuel pump are you running?

[jdmser]

Walbro 255

[gawdzilla]

what engine management are you using? if you're on stock ecu it might be too advanced going so high in boost and the motor is pulling back a lot of it to fend off knock

[Yellow4g63]

He has a tuned ECU. What about your alternator voltage? whats that look like?

[Darius]

I'm thinking there is a combination of things working against you here and it is a good thing you have an EGT sensor to warn you of the problem. It is fairly obvious that the engine is leaning out and you should drop the boost down to 18 psi or lower as the EGT permits. 2100F can melt pistons.

1) The Walbro 255 isn't going to be enough to support that kind of power at 20 psi with <14 V. Upgrade to a Bosch 044 or equivalent.

2) Like yellow mentioned, the voltage to the walbro could be dropping off due to increased load from the fans. Upgrade to a Quest alternator.

[Cjmartz2k]

I have to disagree. A single Walbro 255HP can easily handle anything a T3/TO4e can do, even at only 11.5v. Hard wiring to get 12-13 volts is still a great idea, but I don't think he's running out of fuel (at least not because of the pump.) To little timing can cause really high EGT's also.

[jdmser]

I do not have a egt sensor. I have a autometer coolant gauge(ect) with the sensor tapped into the intake manifold. I have no idea on battery voltage since my lap top died a couple months ago and it's hard to see the lm1 at 100mph. The ecu was tuned by Carl H with a emange to adjust for the Q45 maf. The fuel pump is hard wired to the battery with a fan relay switching it. I did notice this afternoon that there was a small amount of oil on the bottom of the compressor housing.

[Yellow4g63]

I do not have a egt sensor. I have a autometer coolant gauge(ect) with the sensor tapped into the intake manifold. I have no idea on battery voltage since my lap top died a couple months ago and it's hard to see the lm1 at 100mph. The ecu was tuned by Carl H with a emange to adjust for the Q45 maf. The fuel pump is hard wired to the battery with a fan relay switching it. I did notice this afternoon that there was a small amount of oil on the bottom of the compressor housing.

You could just check the voltage after the car warms up and the fans are blowing. pop the hood and attack it with the old voltmeter. Then turn the lights on and check it again.

[rb25drag]

Your Problems are Kinda Similar to mine when I was at the track last, im assuming your still on stock coil packs? Mine is Blowing out the spark when boosting causing it to BOG Real bad, The more I ran it the worse it got.

Also How is your Spark Plugs? The Gaps alright?

You could try a Smaller Gap just too see if it helps not blow out the spark. My coils over the years have been getting weaker B/C I have had to keep lowering my plug gaps till now Im at .023 and the end of my chain. But I think the main cause of my failure is my 2 step was beating on them pretty hard. But just another Idea you can look at.

[DriftingisLame]

Carl left my first tune quite retarded in the top end as it was a new motor, and he had safety in mind for that tune. However, with low timing in top end, the side affect is an increase in EGT. My EGT's will become dangerous if I stay in it for more than 2 gears.

I doubt your fuel pump is not flowing enough, Ive heard hard wired, those are good for 450whp. Actually now that I think of it, me and a buddy have hit 400+ whp with just a 255.

The concern I have with this only happening in 3rd gear is maybe the knock sensor picked up knock in the early gears and pulled timing. This happened to me last time I went to the track, only trapped 1mph faster with 40 whp more.

Have you checked codes?

[Darius]

My bad. For some reason I read that as EGT.

If the Water temp gets up around 100C=212F, the ECU begins to pull timing (5*).

Also, if the alternator cannot keep up enough to supply 11.5V, then that is shifting the injectors along the voltage vs. lag curve to open earlier. It could be running into issues there if the latency settings were not adjusted by Carl to accommodate that for larger injectors. Lower voltage and larger injectors increases the lead time for them to open at the right time.

For reference, the voltage on my hand controller reads at 14.4V before the fans kick on and draw 30 amps and those drop the voltage to about 13.8V. I have never checked to see what my fuel pump actually sees though. That is my future winter project.

And you're probably right, the non-high pressure Walbro may be sufficient at 20 psi of boost at 12V. In theory, it is only able to pump 175lph= 486cc/min/injector under those conditions, which should be adequate for 400+ hp like DriftingIsLame said. But this equates to 67.5% injector duty for 720cc injectors.

Bump that up to 20 psi of boost at 13.5V and the same pump will put out 210lph=583cc/min/injector or an injector duty of 81%.

I'm sure you've seen this graph before, but this is what I'm using for reference:

Why does this image keep x-ing out?? The link is still good.

Modified by Darius at 1:14 PM 8/14/2008
Modified by Darius at 1:14 PM 8/14/2008

[jdmser]

It has had this miss since I did the head and cams but, I have always attributed it to cam noise. It's only at idle though. Once I give it some gas it goes away. I'm going to pull the plugs and see what they look like. I would imagine it's either getting too hot and pulling timing or blowing out spark. I think the nitrous might be keeping it cool enough in 1st and 2nd but, since I'm already in boost in 3rd it's not spraying.

[jdmser]

Ok, little bit of an update. Battery voltage is 14.5v at idle, 13.9 with the head lights on, and 12v with the fans running and the head lights on. Tried to take the car out tonight after lowering the duty cycle on the boost controller. At cruising the afrs are 14.5, at tip in they are 13.5, and as soon as it starts making any kind of boost it leans out bad(14.5 @ 5psi). Pulled the ecu and check for codes but, just got a 55. Bad fuel pump?

[DriftingisLame]

My awesome way of diagnosing fuel pump failures at high load:

Get an inline fuel pressure gauge, and a bunch of fuel line, stick it through your hood by the windshield wipers, so you can see it in the cab, shut the hood (make sure your fuel lines arent pinched. Then take it for a drive and go flat out. If your pressure stays good at normal driving, but bleeds off quickly once the demand for fuel is high (WOT, maximum boost) your fuel pump is bad.

Now go diagnose that biatch!

[jdmser]

With the way it starts sputtering when I get into boost I don't think that way is an option for me.

[Cjmartz2k]

You should see the pressure drop well before it starts studdering.

[gawdzilla]

My awesome way of diagnosing fuel pump failures at high load:

Get an inline fuel pressure gauge, and a bunch of fuel line, stick it through your hood by the windshield wipers, so you can see it in the cab, shut the hood (make sure your fuel lines arent pinched. Then take it for a drive and go flat out. If your pressure stays good at normal driving, but bleeds off quickly once the demand for fuel is high (WOT, maximum boost) your fuel pump is bad.

Now go diagnose that biatch!

great method, i have used it before to found out why my injector duty cycles were so high but my AFRs were not richening. fuel pump was dropping off pressure.

[240z4u]

Are you injector lag settings set correctly? I had a hell of a time until Darius tipped me in on this situation.

Sounds to me like your blowing out spark, and igniting the fuel in the exhaust manifold.

Evan

[gawdzilla]

what do you mean by "wont rev" past 1st and 2nd gears?

is it breaking up and stuttering, or just not pulling as hard with a normal exhaust tone?

[jdmser]

It would run fine in 1st and 2nd then lose power with normal exhaust tone in 3rd. By the end of the night it was breaking up and stuttering in 3rd. Now it is breaking up, stuttering, leaning out when it gets any where near boost. I made a few changes that I don't think are related but, you never know. I went to a Gizzmo IBC, changed oils from M1 15w50 to Royal Purple 10w30, replaced gear oil, and cleaned off negative battery cable end. It had been running fine on 18psi until this point.

[jdmser]

Tried this out a little while ago. I can say with almost 100% certainty that it is not my fuel pump. Fuel pressure was 40psi at idle, 50psi at cruising, and 60+psi when I got into boost. I would assume this means I am blowing out spark. I just thought it would go real rich if it was but, I did see it dip into the 11.5 range a few times right before it would start to break up.

[rb25drag]

Did you drop the boost any?

Yesterday I messed with mine again, I put it back on stock 7psi boost and Took a Ton of fuel out of it, Got it to finally hold RPM's all the way to 6500, but it was still running rich 10.8 A/F, But as I was pulling back in the Driveway after a Few pulls, It started Idling up and Down and my a/f readings were going from 14.5-10.0, It was pig rich and then super lean at idle, cut the car off and started it back up, Idle was normal again.

So I know I was blowing spark out in High Boost, so that leads to my coils, But im not sure what was up with the idle, Never had it to do that before. I think my coils are just killing it.

[jdmser]

I took out some but, I don't think is was enough. At anything over 5psi it would start to break up. I haven't changed my plugs yet so on my next day off I'm going to through in a new set and gap them down a little.

[rb25drag]

What Heat range of plug are you running?

[jdmser]

7s

[rb25drag]

hmm, might try going down 1 range and trying that.