N/A Dyno w/ JWT Turbo 50lbs/cobra/walbro 255lph LEAN?!

[brage]

Well, I bought a used JWT/MSD 50lbs/Cobra MAF from gwong on the board here, and everything looked to be in perfect condition. I know he was running 8.5:1 compression, and I am running stock compression but he didn't think the JWT ECU was programmed for the 8.5:1 compression. I installed the F-Max kit with the fuel system about 2 weeks ago, and blew ALL FOUR ringlands after 4 days of boosting at 7psi. I dynoed the car the night it blew at 224RWHP, but the wideband O2 at the shop was out of service at the time.

So out comes the motor, in goes a nice clean motor out of a '97 with 36k miles. I decided to run this motor N/A until I confirmed that the engine was in good condition. So now the engine is running N/A with the JWT turbo 50lbs/cobra program N/A. With the cobra maf, and MSD injectors of course.

Long story short it dynoed at 150RWHP N/A last night, but the A/F ratio is jacked... it got up to 14.5:1!!!!

Anyone know if this is something to do with running the ECU N/A? It shouldn't really have anything to do with it

Any info would be greatly appreciated. Unfortunately I didn't print the dyno sheet... but I might be able to put it up in the next couple of days.

BTW this is using the stock FPR on the JWT fuel rail. Do I need to bump up the fuel pressure ?

-jeff

[andrave]

what pressure do the MSD injectors need? could very well be an explanation.

[sykikchimp]

Is it a 3 bar or 4 bar fuel program?

Are there any codes stamped on the ECU from JWT that you could call them and ask about specs on it?

[brage]

I called JWT and they had me pull the ECU and get them the hand written # off of the chip on the daughterboard... They are checking the program to see what is on there. I'll let you guys know what the deal is. BTW there is no sticker on the ECU that says 4 bar program.. They also said the 8.5:1 compression program just sets the timing a bit more aggressively

-Jeff

[Jeff240sx]

My money is a 4-bar program, which requires the use of an aftermarket fuel pressure regulator. Sorry to hear about that man.. I guess we all gotta blow an engine at some point
-Jeff

[brage]

Well, according to JWT my ECU has the standard 50lbs+cobra MAF turbo program... So my problem must be elsewhere.

Looks like I'll be checking ...
Timing,CAS,MAF,FPR,plug gaps,o2 sensor,TPS

Any other things I should check?

-jeff

[Jeff240sx]

Pump, injectors, fpr, anything at all fuel/spark related until you can pinpoint the problem.
-Jeff

[Var]

Originally posted by brage
So out comes the motor, in goes a nice clean motor out of a '97 with 36k miles. I decided to run this motor N/A until I confirmed that the engine was in good condition. So now the engine is running N/A with the JWT turbo 50lbs/cobra program N/A. With the cobra maf, and MSD injectors of course.

Long story short it dynoed at 150RWHP N/A last night, but the A/F ratio is jacked... it got up to 14.5:1!!!!


-jeff

I dont get it..what was the problem exactly? 14.5:1 is a good a/f ratio. Are you saying that it should be running rich because you're using the turbo fuel mapping?

[brage]

Originally posted by westboroughpimp
I dont get it..what was the problem exactly? 14.5:1 is a good a/f ratio. Are you saying that it should be running rich because you're using the turbo fuel mapping?

"Normal" for our cars is ~11.5:1... I'm going to put the kit on and bring it to the dyno tomorrow night. I'll let ya'll know how that goes

[Var]

Originally posted by brage
"Normal" for our cars is ~11.5:1... I'm going to put the kit on and bring it to the dyno tomorrow night. I'll let ya'll know how that goes

ummmm NO? What the hell. 11.5:1 a/f ratio??? you're running too rich. Have you heard of Stoichiometric ratio? 14.5:1 for all cars. That's the ideal and most efficient a/f ratio for pump gas. at 11.5:1 our cars wouldn't pass smog. If i'm trippin then i take my smog license away from me.

Maybe i misuderstood. By "our cars", did you mean my car too? or did you mean your car with the upgraded injectors and ECU. if you mean a stock 240, then i dont think theres any way it has 11.5:1 a/f ratio.

[brage]

Originally posted by westboroughpimp
ummmm NO? What the hell. 11.5:1 a/f ratio??? you're running too rich. Have you heard of Stoichiometric ratio? 14.5:1 for all cars. That's the ideal and most efficient a/f ratio for pump gas. at 11.5:1 our cars wouldn't pass smog. If i'm trippin then i take my smog license away from me.

Maybe i misuderstood. By "our cars", did you mean my car too? or did you mean your car with the upgraded injectors and ECU. if you mean a stock 240, then i dont think theres any way it has 11.5:1 a/f ratio.

ok so maybe the asshole that lead me to believe that 14.5:1 was lean should be shot

Thanks for the input. For now I'm not too worried about the A/F ratio. I'll just make sure to keep an eye on the EGTs!

Thanks,
Jeff

[Jeff240sx]

There is stoichiometric, a mathematical number, that doesn't take into account ignition, compression, or any other variables, and then there is adding a turbo. If you run to 14.5:1 under boost, then there is a very real chance of detonation, and another engine grenaded. Turbo should run in the 11.5-12.5:1 range, depending on power. High compression, nitrous, advanced ignition all need richer mixtures to not have the fuel explode before it's supposed to.
-Jeff

[andrave]

I agree, lower is safer.
that "lean is mean" shit doesn't apply to a street driven turbo. (it actually doesn't apply at all).

[rednerd]

If you run 14.5:1 under full load you WILL detonate the crap (rings) out of your engine. Do a quick search for dyno runs with an a/f graph. You will see that the ecu map richens the fuel quite a bit once the engine hits load/boost. In fact a lot of cars won't even look at the O2 sensor at WOT. 12.5:1 is the very leanest you want to run at the top end under boost.

Your engine will try to maintain an a/f mixture closer to 14.7:1 when the car is at idle or cruising and there isn't a load that might cause detonation.

[brage]

Ok, I put the turbo back on the car and brought it to the dyno. The A/F ratio isn't 14.1:1 across the board, but it does run 14.1:1 under 4000rpm . After that it richens to ~12.0:1 FAST. I am still very concerned that it is running so LEAN even tho I don't really hit boost until ~3500rpm... Also I seem to be having quite a bit of backfiring when letting off the throttle. Any ideas what this could be in relation to? Crappy f-max perpendicular bypass valve return? MAF too close to turbo intake?

Here is a pic of the setup:

[Jeff240sx]

Bingo! One problem, that I also had, is that your MAF is WAY WAY WAY too close to the compressor. There needs to be a 18" separation between the back of the MAF and the inlet of the compressor. My car shuddered, backfired, and just plain ran-like-crap. So, I called JWT and they instructed me to move my MAF. Since then, its ran like a car. Try that with a piece of PVC or something (just to test before spending $60 on a custom pipe) and see if the car runs better with the MAF further out.
-Jeff

[brage]

Originally posted by Jeff240sx
Bingo! One problem, that I also had, is that your MAF is WAY WAY WAY too close to the compressor. There needs to be a 18" separation between the back of the MAF and the inlet of the compressor. My car shuddered, backfired, and just plain ran-like-crap. So, I called JWT and they instructed me to move my MAF. Since then, its ran like a car. Try that with a piece of PVC or something (just to test before spending $60 on a custom pipe) and see if the car runs better with the MAF further out.
-Jeff

That shouldn't effect the lean condition though, right? Just the backfiring, etc?

-jeff

[sykikchimp]

Most JWT Fuel maps I've seen run exactly as you said. ~14:1 below 3500-4000 rpm, and then a fairly sharp drop to 12:1. Are you getting any audible knock?

[brage]

Originally posted by sykikchimp
Most JWT Fuel maps I've seen run exactly as you said. ~14:1 below 3500-4000 rpm, and then a fairly sharp drop to 12:1. Are you getting any audible knock?

No audible knock...
-Jeff

[sykikchimp]

Originally posted by brage
No audible knock...
-Jeff

hmm... do you have an EGT or A/F gauge? maybe keep an eye on it if you feel nervous about it, but I don't think I would worry about it too much. Get your bogging problem fixed, and I'd bet you have no more problems.. for a while at least..

[INeedNewTires]

the Stoichiometric ratio is actually 14.7:1 just puttin in my 2c. interesting thread!

[Var]

Originally posted by Jeff240sx
There is stoichiometric, a mathematical number, that doesn't take into account ignition, compression, or any other variables, and then there is adding a turbo. If you run to 14.5:1 under boost, then there is a very real chance of detonation, and another engine grenaded. Turbo should run in the 11.5-12.5:1 range, depending on power. High compression, nitrous, advanced ignition all need richer mixtures to not have the fuel explode before it's supposed to.
-Jeff

yes i know but 14.5 to 1 is great for a stock 97 ka, the motor that was tested. right?

[sykikchimp]

Originally posted by westboroughpimp
yes i know but 14.5 to 1 is great for a stock 97 ka, the motor that was tested. right?

his car is running a JWT Turbo ecu.. not stock.