engine cut on dyno only

[DOHCAccord]

Ok, heres a weird issue and im inclined to believe the guys at the shop. I was on the dyno this last saturday and at 5k rpm in 4th the engine just hits what seems like a rev limiter. I adjusted everything in my laptop making sure nothing was causing it. A total of 5 pulls later and each time it hit like a brick with the engine popping. The afr showed it going form 12-1 up to 13--1 then spiking to 14-1 at the engine popping. i iknow its going lean and part of those runs was to see how it was stacking up. now, i drove the car for months without issue, and that day i made mulitple highway pulls setting my boost controller with out a single issue. I pulled the car off the dyno, hit the highway and a full pull. no issues at all. the guys think it running out of fuel, but i dont know yet.im awaiting my fuel pressure gauge and then ill know if its dropping pressure, but its sappose to have a 255 walbro high pressure, again sappose to by a shop i though i could trust. what do you guys think.

 

[JusMX141]

Uh, 14:1 under hard acceleration is retarded lean. You're definitely running out of fuel....it's a good thing you didn't keep pushing it.


What car are you talking about? What supporting mods? What are you tuning with? These things should've all been answered in the initial post.

 

[DOHCAccord]

sorry, bout the lack of info. its a 97 accord, i know its not a dsm, but i run a 2g dsm ported turbo manifold, 2g o2 housing ported to 2.5 inch, ported evo3 16g and dsm 450cc blue top injectors.

I follow the dsm world about the hard parts and setups since its so easy to make power with a dsm, also mr peepers has helped me with my porting and boost creep.

i thank you for your reply. do you think its just tuning or fuel pressure thats the main issue.

 

[EclipticalGS]

Im not understanding why you think think its fuel cut. This happens only when on dyno...if it were really fuel cut it would happen out the street too. The people dynoing your car must be doing something wrong like adding too much of a burden or load on your wheels causing it to bog and not be able to have the hp to keep the dyno spinning faster. so you cant make it to your top rpm... But im not sure as to i dont really know about dynos. This jsut seems where that fuel cut disapepars when on the road..i guess your cars inertia is gonna keep it moving no matter what. Do you have a turbo? Do they run a fan on the intercooler while your pulling. do a 3rd gear pull and see what that makes. Just some input, they might have a messed up dyno....

 

[DOHCAccord]

yeah its a evo3 turbo, they said it was fuel related and the afr was creeping up to way to lean, they ran a bunch of cars prior to mine that dont make really the power i do, 238whp 247wtq at 8 psi, yes a fan was on the front. its weird, they said its happened before to cars that ran out of fuel, either pressure or just in the tune. basically pegging full lean and popping and then they just kill the run. i do plan to have it retuned for more power and to check the afrs, but i just wanted to see what you all might toss in either the tune or pressure

 

[JusMX141]

This isn't related to your car being lean, but it's something you may want to hear about if you decide to go way richer in order to be on the safe side.

Now I don't know ANYTHING about Hondas, but I'm going to word this in terms that myself and other DSMers can relate to. I've seen cases where a dyno can really mess with your tune because of how your fuel trims are set up before boost begins to build....especially cars with monster turbos that take a long time to spool. Here's why:

When you get on it hard on the street, you're generally in a lower gear and the power builds quickly because the engine has the ability to rev almost instantly. Your off-boost tune on the street is barely noticeable when you rip on it.

When your car's on the dyno, the operator will take the car up to a predetermined RPM in whatever gear they dyno in- generally third. When they dyno run begins, the operator will mash the throttle to the FLOOR, literally DUMPING fuel into the engine even though it's still under it's boost threshold where the added airflow will gobble up the additional fuel. The car may even choke out or sputter, which ruins the run. The ECU sees knock, timing gets pulled, and you just made about 60whp less than you should've.



If you think your on-boost tune is where it should be, work on your off-boost tune when you're on the street. Practice getting the car at about 3k in third with no boost and then floor it, and see how the car responds. Lean it out accordingly to aid in making your dyno run a little more enjoyable.

 

[EclipticalGS]

I second all of that ^^^. Do third gear pulls first. then see waht you get from 4th gear. On-boost tuning may be good from waht i hear..But your off boost tune sounds pretty bad. but when i mash my pedal on my turbo'd civic, it is street tuned nicely before it hits boost. Then boost takes over and thats a whole different tuning set-up. Richening, leaning. Timing retardation. Amount of fuel at certain rpms, WOT fuel...etc.etc. What are you using to tune your stuff. Is the problem that you can't get the fuel to the cylinders that you are trying to tune?? Tell us what you find out from that pressure gauge ### if its low,Updgrade fuel pump/ecu. however you want to do it. ONLY if it is a fuel cut!! But from what im hearing Jusmx141 is right. ### when your on the highway, i doubt you mash pedal to the floor..?? No, You take it easy and feather it out and get up to speed slower. OFF-boost tuning will really help daily driving too when u stick at low rpm's . Use an EMS system. try to add more pressure when throttle is at WOT. Then do a pull. Just experiment!!

 

[DOHCAccord]

good information and it sounds like that could have been it. i will get the fuel pressure numbers up and go forward from there. i use honata s300 to tune my setup, well i didnt tune it, it was tuned for me. i will let you all know what i find and thank you all for your input