were did my boost go!?!

[spocks90talon]

whats up guys, ok i bought i new project 91 gsx, its got a evo 3 16g, walbro 255, new 2g mani, 2600 clutch, 3 in intake pipe and that lovable stock mas just to name a few mods . ok the problim is in 2nd gear i can put it to the floor and and it pulls like a mother and my aftermarket boost gauge reads about 11-12 psi (stock) but when i first put it down it will boost up to 14- 15 just for a split second then go back down to stock boost (boost surge) after that it will pull for a while than at about 4500 to 5000 rpms it feels like its loosing boost but the gauge still reads 11-12 psi, its like it just pulls the hell outta you then as the rpms rise it tapers off, why is it doing this? the motor runs strong all stock internals, good compresson, no boost leaks. one thing i thought it might be is the car is dumping the bov to the atmosphere with the stock mas which we all know is a no no, oh ya it has the crushed 1g bov too. i was gonna go to the junk yard and find a stock intake pipe if i could and recirculate the bov and see if thats the problim but could the car just need tuned? i didnt think so saying its still got stock injectors i beleave and im still running stock boost but im just now starting to learn about air/fuel tuning and dont know much. oh and another thing it really only does it in 2nd and 3rd gear, 1st pulls the hell outta you and 4th and 5th seem to hold boost just fine help guys i dont wanna spend money on shit i dont need to!!

 

[toybreaker]

It sounds like there's trouble coming.

When you start changing pieces on these cars, you have to look at the bigger picture.

There's some nice pieces already there, but the injectors and maf will limit the car to around stock fuel apportioning/delivery. If you're putting in more air, you'll overrun what the maf can measure and the injectors can deliver, and then it's going to go lean, get hot, and start frazzling pistons/exhaust valves and the like...

I am not a tuner, so I can't tell you what to do.

I'm thinking the ecu is seeing knock, and pulling timing and/or disabling the boost control solenoid. Have you hit fuel cut yet?

I can tell you that you'd better start by matching the fuel flow to the increased air flow capability. An adjustable fuel pressure regulator will get things headed in the right direction

A 255 will flow the volume, you just need to match the fuel pressure to your boost levels, and an adjustable fpr can do that for you.

Dsmlink will allow you to monitor a/f ratio's and more importantly, knock. It's one of the first things I would buy, in fact, as it can be adjusted for the mods as they are installed, and so won't be outgrown quickly.

Not recirculating won't affect the performance under boost, it'll just mess up the driveability, especially right after a shift, after all that measured air goes "phhhht."

Hopefully, someone has more experience will be along to give to better advice.

I would get ALL the paperwork, reciepts, and everything the previous owner has related to your car. Write down all the mods he's installed, and give the car a thorough look over, to see if he's forgotten anything.

I would also perform any and all maintainance that needs to be done. T-belt, cooling system, brakes/suspension and all the fluids should be inspected/changed/serviced ASAP, long before any more mods are added.

Modifiying things is all fine and dandy, as long as a logical proccess if followed. Skipping a step can have disastrous effects. There's a pretty nice series of upgrade paths on almost every dsm site. I would read every single one I could, and notice the trends/patterns. This is all tested information, verified by real world experience.


I just don't want you to have a meltdown in the meantime.

Speaking only for myself, I can't resist nailing the throttle every single chance I get... ...which is why I'm happy to accept less ultimate performance, because I can use everything the car can make, anytime, anywhere, without fear of creating some "interesting" ashtrays that used to be pistons...

 

[spocks90talon]

hmm interesting, no i havent hit any fuel cut at all, the t belt is only about 5k old, it runs strong but i do notice that it has a lot of lifter noise, now ive had a few of these cars and i know they all kinda do that but this one will tick tick tick for 10 or 15 mins even after its warmed up all the way then suddenly it will just go away, as for running lean i think it might be, the car does run slightly hotter than my other turbo's ive had, it never over heats but my other dsm's all liked to chill around the middle of the temp gauge and this one sits just past the little temp symbol on the gauge but doesnt really move much oh and this one warms up ALOT faster, in like 5 mins or less just normally driving it without boosting it. oh and it is sucking down gas like crazy too which is another thing i noticed. so a fpr will help? i dont know if its knocking but the check engine light never comes on, i gave the car a real good look over yesterday, didnt see anything that looked bad, this one looks like it was fairly well taken care of, i gave it a tune up too, the old plugs were kinda heat glazed but not bad. i dont know but i dont want to blow my motor up! it does have like 145k, anything else i can do to save it!

 

[GVR4592]

Why don't you have a datalogger?

 

[spocks90talon]

i just havent had the car that long, not even a week yet. so do you guys think a fpr will help my running rich problim?

 

[toybreaker]

Matching the fuel flow to the airflow is the key.

You really only need more fuel under higher than stock boost levels.

Glazing the plugs is something that happens when the plug is getting hot enough to melt the deposits that naturally occur during engine operation. It might be a good move to go one heat range colder on the plugs to prevent a reoccurance. It is also an indication things are starting to get toasty...

I don't feel qualified to flat say you need an fpr, but increasing the airflow will require more fuel, and the factory set up will begin to get overtaxed right around where you are.

At some point you will have to make a command decision about how much boost you want to run.

That will dictate the mods you will need to support the boost level/airflow/fuel requirements.

At the least a datalogger set up is one of the first things you will need...Good call, GVR4592.

It will show you where you are, and what, if any, fuel mods may be required to keep things safe at your present boost levels.

That, and they're really cool/educational to play with.

 

[spocks90talon]

ok, where can i get a good cheap datalogger?, i dont have much money to play with right now so... maybe 200 or 300 bucks, im gonna get a fpr in the next couple days, as of right now, i dont want to run more than maybe 18 or 20 psi because of all the miles and stock internals, i know they can handle that but i dont want to blow this thing up because im trying to make it into a reliably, fast, daily driver, i would be happy with 300 to 350 horse right now but after i get the engine built im gonna shoot for 450 to 550 horses