Rep Power: 281

ok so when im low gears like 2nd and i nail the gas when the boost climbs over 5psi i get some hesitation/backfireing/hiccuping from the engine, almost like the boost is goin in and out or spiking, but its not. mabey the engine cant keep up? but if that was true it would be a common problem and i havent seen it yet, anyone have the same thing goin on?

 
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your clutch isn't slippin is it? Otherwise, maybe your wastegate is flippin open and close...thats a hard one...

 
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mu car would do that too...hesitate and studder a bit at like 5 psi. So I checked my fuel pressure and I wasn't getting the fuel I needed under boost. Waiting on new FMU so I can get it going again and then tune with my emanage.

 
Rep Power: 281

yes you know what it might be my clutch slipping, i mean i just bought the ACT clutch to put in cause my stock one took a ****. but funny thing is when i watch the digital boost reading its not really dropping that much? it is a hard one

 
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what fmu did you have??? i got the stafford one

 
Rep Power: 584

if ur clutch is slipping u can press the gas and go no where, since ur moving i doubt it, ive had this problem so MANY MANY MANNYYYYYY times, its strictly a fuel issue, if ur moving the boost up, and not accounting for that with fuel, ur **** is leaning out and its falling on its face. and doing exactly what u are doing. its all tuning my friend do it and do it better

 
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i have the stafford...waiting on my 4th actually....yes 4th new FMU from SF.

 
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each one had had problems with multipliying fuel

 
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ok i rethought my statement, is the car spitting black smoke out when this happens. considering the quote my rethinkin was right, RICH, need to ditch this inline pump right next to the FMU, and that vortech fmu SF uses is horrible, i have one under my bed in my room, my shop refused to use it for that reason, AEROMOTIVE is what i have right now, and an intank PUMP

 
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Bad tuning will cause hesitation.

 
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yes I think we know this.....thanks for the help tho.

 
Rep Power: 281

ok so the fact that is untuned and also the fact that im using a stafford FMU will cause this hesitation? you guys got a link to another FMU, im kinda in the dark about them...

 
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He asked why it was hesitating. I told him.

 
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Adjust fuel & timing appropriately. You may need to retard the timing a couple degrees.

 
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i had to retard my cam gear 2 degrees for my setup.

 
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Its not the clutch, its either fuel or timing (i know it was mentioned)

Hook up a fuel pressure gauge to see if its the fuel. This will narrow it down. Is pressure rising correctly? Does it peak and drop, does it keep rising? Did you screw with timing at all?

Cam gear timing has absolutely nothing to do with it. Thats cam timing, not ignition timing. Did you put one on and not time that right?

questions questions.

And I would argue that Vortech FMU's are not a POS, the SF design is a POS....

 
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Wouldn't the EGT gauge be reading the lean condition? Why is this such a mystery for this guy.(Not trying to flame or put you down Im just wondering if you don't have that gauge or something to that affect.)

 
Rep Power: 584

EGT= exhaust gas TEMPERATURE

needs a wide band O2 to really tune it good, a basic AF guage aint gunna cut it for ya

 
Rep Power: 281

yeah i got a cam gear, i installed it when i did my head gasket, but i had clearence issues, the bolts on the back of the gear were hitting the head! so i put the stock one on..... i havent got it tuned at all, i have no air and fuel computer, im just goin ***** to the wall with a boost controller. Exturbo, did you have the same problem as me? hesitation under heavy boost?

 
Rep Power: 281

and no i dont have a egt guage, all i got is a cheap autometer af guage with no wide band sensor, so i cant really tell whats goin on in the exhaust. i imagine its a fuel problem, or timing, mabey i f-ed somthing up when i did the headgasket - - ?

 
Rep Power: 584

ok dude stop right there, u have no fuel computer and u HAVE A BOOST controller, both of those are huge problems one the AF computer means u cant tune and two the BC means u can increase at will and that is obviously not working to well right now for u. first off u need a fuel computer to start with. then u should have went and got the boost controller, to heck with the cam gear for now, IMO sell that and use the money for a AFC or something that u can tune urslef if u know how, if not get emanage and then ull be set

 
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Retarding timing however may not be the best solution for his problem...if he is certain that his car is running rich (which in all honesty he probably doesn't unless he's got a wideband meter), pulling timing will multiply the problem he has wouldn't it??

First things first -> it never hurts to get out the timing lamp to check base timing (I assume you've done this...well hopefully!!)

Secondly: is the problem occuring at partial throttle or WOT..??

Being to rich will cause the car to buck and car on, as well will a lean condition...the only way you can truthfully tell is by purchasing a wideband 02 meter and using it's display to tell you..300 bucks for a PLX meter is what i call 'cheap motor insurance'

Your MAP sensor could also be reading a wierd voltage, causing the the ECU to pull timing as well...this would cause the same problems you ahve

 
Rep Power: 281

good advice, i think my problem lies more in tuning then anything else, i think i will invest in a fuel and air setup. the problem is at wide open throttle, and no where else. i mean dont get me wrong, i aint boostin like 500 psi, im only running like 8 or 9. i have the synapse missing link so i dont think that is the problem, i had the stafford one, and i know what it feels like when the map ****s up....i aint messin with the timing, i think its a fuel computer for christmas for me!

 
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Good choice...remember even at 4 or 5 pounds, a poor fuel setup will be your daddy!