knock

[420a-t]

i just recently turboed my 420a and was wondering if i would experience any knid of knock with a stock fuel system and a 12:1 fmu if i keep the boost under 6 or 7 psi? i was trying to search for an answer but all i found was people saying to "just upgrade then you wont have to worry about it"

 

[baxsom]

There is no definitive answer. It depends on the type of gasoline you use, condition of plugs, wires, etc. The short answer is probably not.

 

[BigRand]

Keep the fuel at least 91octane and above, keep the spark plugs w/ some basic $2 NGK plugs, and keep the injectors stock.

 

[VelocitàPaola]

And don't forget a Walbro 190 or better. If you listen to what everyone else has said, you'll most likely not experience any knock.

 

[420a-t]

alright thanks. is my stock fuel pump ok for a couple weeks until i get the money? also, i have an a/t and was wondering if the extra hp would do anything to my tranny. nothing out of the ordinary has happened yet, but i just want to make sure...

 

[VelocitàPaola]

I wouldn't boost much with your stock fuel pump... try to restrain yourself from boosting more than 1-2 psi for now; running too lean would really suck for your engine.

Your tranny should be fine - they're pretty stocky units from the factory.

 

[420a-t]

alright i have another question- i was wondering what harness i should get if i were to purchase a turbo timer. has anyone put a tt on a 420a? i was trying to search for it but i couldnt find anyone who reccomends any harness. i just thought i'd ask while im on my own thread...

 

[BigRand]

alright thanks. is my stock fuel pump ok for a couple weeks until i get the money? also, i have an a/t and was wondering if the extra hp would do anything to my tranny. nothing out of the ordinary has happened yet, but i just want to make sure...

Invest in the fuel pump asap, less troubles to worry about.

As for the tranny, just stay away from those famous neutral drops, and it'll be just fine.

 

[DSMcrazy3]

alright i have another question- i was wondering what harness i should get if i were to purchase a turbo timer. has anyone put a tt on a 420a? i was trying to search for it but i couldnt find anyone who reccomends any harness. i just thought i'd ask while im on my own thread...

There are a few 420aT's with turbo timers, I believe the harness you would need is the same as for GS-T/X, as the ignition wiring should be the same, don't quote me on it though. However, I would suggest a Viper alarm system(791XV) depending whether or not you have a nice place that doesn't overcharge. I got one and it has a turbo timer built in as well as many other features. Some will argue that aftermarket alarm systems will eventually cause problems with wiring, shorts, etc...but if a car didn't come equipped with one, I highly recommend getting one, especially these days and after you have a turbo on the car.

My alarm + install was $250.

 

[GSGoinFast]

There are a few 420aT's with turbo timers, I believe the harness you would need is the same as for GS-T/X, as the ignition wiring should be the same, don't quote me on it though. However, I would suggest a Viper alarm system(791XV) depending whether or not you have a nice place that doesn't overcharge. I got one and it has a turbo timer built in as well as many other features. Some will argue that aftermarket alarm systems will eventually cause problems with wiring, shorts, etc...but if a car didn't come equipped with one, I highly recommend getting one, especially these days and after you have a turbo on the car.

My alarm + install was $250.

Josh is right, I used the greddy harness for the 2g GS-T and it worked perfectly.

As for your fuel pump, don't even bother with a 190. You need the walbro 255 lph HP(High Pressure) model. Think of how high the fuel pressures are with a 12:1 fmu at 8 psi. Anything over 8 with the HP and I run lean, I don't think the 190 could keep up.

 

[VelocitàPaola]

Anything over 8 with the HP and I run lean, I don't think the 190 could keep up.

I don't think it's the fuel pump's fault you're running lean. In fact, I don't think the fuel pump has anything to do with it at all; your tiny injectors are creating the bottle neck here. You can only squeeze so much fuel out of them, no matter how high the fuel pressure is.

I think that the 190 is fine; the 255 and 255HP are overkill, but having either of them won't create any harmful effects (I have the 255, personally).

And besides, once you upgrade (or... should I say, if you upgrade) the fuel system, you won't have to deal with these insanely high fuel pressures anymore. The next step is a S-FMU with larger injectors, which operate on much lower pressures. After that, you're looking at a complete stand alone unit, that operates on even lower pressures.

 

[GSGoinFast]

I don't think it's the fuel pump's fault you're running lean. In fact, I don't think the fuel pump has anything to do with it at all; your tiny injectors are creating the bottle neck here. You can only squeeze so much fuel out of them, no matter how high the fuel pressure is.

I think that the 190 is fine; the 255 and 255HP are overkill, but having either of them won't create any harmful effects (I have the 255, personally).

And besides, once you upgrade (or... should I say, if you upgrade) the fuel system, you won't have to deal with these insanely high fuel pressures anymore. The next step is a S-FMU with larger injectors, which operate on much lower pressures. After that, you're looking at a complete stand alone unit, that operates on even lower pressures.

I disagree. Think about it, at 8 psi the 12:1 fmu is raising the fuel pressure 96 psi. Look at the flow patterns of the Walbro pumps below. The 190 doesn't look like it can keep up.

 

[VelocitàPaola]

I disagree. Think about it, at 8 psi the 12:1 fmu is raising the fuel pressure 96 psi. Look at the flow patterns of the Walbro pumps below. The 190 doesn't look like it can keep up.

That still doesn't quite make sense to me. The 12:1 FMU is supposed to add 12psi of fuel pressure for every 1psi of boost on top of the base idle fuel pressure (47-50psi). So, at 8psi of boost, your fuel pressure is anywhere from 143psi-146psi.

I assume that the X-axis on that graph represents fuel pressure at the fuel pump outlet, not in the rail; that may be where the descrepancy is.

 

[420a-t]

alright i will invest in a fuel pump asap. one other problem- my car was boosting fine until about a week ago. my boost gauge reads vacuum fine but then stops at zero. i told paul this, but i forgot to say that my 14b's wastegate is cut and is now adjustable. i already checked for boost leaks too-any suggestions?

 

[BigRand]

well if you checked for leaks,then your not finished.

Check to see exactly what your vaccume is reading at idle. If its "lower" (meaning from zero counting up) then usual then you've probably got a leak, or a intercooler coupler that is letting air out somewhere.

Also it could just be a gasket problem (I'm pretty sure you said your internally gated) so check for exhaust leaks by the manifold. (does your car sound louder than normal?)

And last but not least, your wastegate mod could have failed, and might be opening to early, and not letting any boost build up. I'm not going to lie, I understand how to deal with external gates more than I do internal.

 

[420a-t]

ok i checked everywhere for leaks and i couldnt find any. my mod i did to my wastegate made it so it was always open a little, (unlike a spring) but i dont think thats the probelm either.

i had it dumped to the atmosphere first, and when it started to read no boost a couple days later i closed my wastegate all the way to see if it was the wastegate. it wasnt opening early because it was a drastic change in sound when it was opened to when it wasnt and my car sounded like it did before i turbo'ed it. im so confused...

also, when i first finished my car, i had the boost up to about 6 or 7 psi on my stock fuel pump...it didnt seem like anything was wrong with it, but since i didnt have enough fuel, do you think i knocked a ton? what other damage could i have done?

 

[GSGoinFast]

ok i checked everywhere for leaks and i couldnt find any. my mod i did to my wastegate made it so it was always open a little, (unlike a spring) but i dont think thats the probelm either.

i had it dumped to the atmosphere first, and when it started to read no boost a couple days later i closed my wastegate all the way to see if it was the wastegate. it wasnt opening early because it was a drastic change in sound when it was opened to when it wasnt and my car sounded like it did before i turbo'ed it. im so confused...

also, when i first finished my car, i had the boost up to about 6 or 7 psi on my stock fuel pump...it didnt seem like anything was wrong with it, but since i didnt have enough fuel, do you think i knocked a ton? what other damage could i have done?

I would do a compression test to see if you did any damage. As for the leak, does it feel like you have boost or no boost? I know my boost gauge broke so it would only read like 1-2 psi tops even though I was boosting 6-7 and the vac still read fine. Also, if your wastegate is open all the time, that could be it too. Why didn't you just do a spring mod? There are 4 possible reasons why you aren't seeing any boost.
1) broken boost gauge
2) broken or improperly working wastegate
3) Massive leak
4) turbo is completely siezed and not spinning at all.(probably not)

 

[420a-t]

alright now i have another question: i got bored and decided to put a BOV on. even though im not running any boost, shouldnt it still work at zero vaccum or am i turning into a stupid ricer because i want the oh-so-cool sound? by the way it's a 1g bov...thanks for any help

 

[XMasta19]

"A blowoff valve is a vacuum operated valve that is located after a turbocharger on an internal combustion engine, but before the throttle body butterfly valve and intake manifold. Its use is to vent extra pressure being developed by the turbocharger when the throttle is closed, such as during a shift. During a shift in a car with a manual transmission, the throttle plate is closed. The pressure produced by the turbocharger has nowhere to escape to, thus blowing-off before before making it's way back to the turbo, aka compressor surge....."

So you see...if there is no boost, no cool ric0r sound