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View Full Version : more boost in 1st and 2nd?



Lagos
12-18-2004, 03:52 AM
when daily driving around, my car makes no boost in 1st gear, and some boost in 2nd. i know that boost is load dependant, but i have seen videos of 3sgtes getting 10 psi in every gear.

im thinking that a lot of it must have something to do with the exhaust system. a car with upgraded downpipe and 3in exhaust should make more boost in 1st and 2nd gear, but what about the tvis system? since all my daily driving is done under 4k, im starting to think that this is whats making it harder for the car to build boost?

T-spoon
12-18-2004, 05:13 AM
Hmm, dunno, I get noticable boost in every gear. With the car overheating if I boost, I've been short shifting at like 3k rpm and evenso if I'm not careful there's enough to activate the BOV. As far as I know TVIS is still working on my car, exhaust is just a two foot long 3" pipe. I'm checking my timing though tomorrow, there's some chance it's way off which would explain some of the peculiar behavior from the car. I wouldn't think TVIS would be inhibiting boost building, the alltrac I had would build boost very quickly in first and second before 3k. How much throttle are you giving it? If you build up speed/rpm slow enough it doesn't build boost, you can keep it hovering around 0 pressure/vaccum.

91jdmcelica
12-18-2004, 05:36 AM
it makes no boost at all in 1st gear? thats definately not normal. One way to narrow it down to the TVSV would be to cap off the end going to your wastegate actuator from the TVSV. Just leave the vacuum line coming from your turbo compressor housing to your wastegate actuator. Almost the same way you would set your actuator up for a manuel boost controller.
If you try that, you should definately get boost in 1st gear.

-Kyle

Lagos
12-18-2004, 05:56 AM
remeber guys...im talking about the T-Vis. not the T-vsv. during daily driving i shift under 4k. so that means that only 4 runners are open on the intake manifold. would there be any way that having 8 runners open at all times would help generate boost faster?

skreem
12-18-2004, 06:20 AM
maybe its ur fmic, all the extra piping has to have some effect on boost.

Aust162
12-18-2004, 07:11 AM
i can make 6psi+ boost in 1st gear. you have to really step on it thou.. i only boost in 1st while dragging, or else it just destroys my tyres even more ;)

Luni
12-18-2004, 05:37 PM
Yeah my turbo is fucked and I still get 2-3 psi in 1st gear.

You have something wrong.

Snafu
12-19-2004, 12:42 AM
Was it doing this before too? or has it just become a problem recently?

Dumb question, but is your airfilter doing alright?

Lagos
12-19-2004, 04:14 AM
basicaly it feels like a have to floor it to genetate 10psi in 2nd-3rd. in 4th and 5th, the boost comes on with less effort. so i think im looking into a reason why ive seen some mr2s or 5sfTes spool up to 10 in almost every gear without having to go WOT.

Luni
12-19-2004, 04:21 AM
When my turbo worked and there were no leaks I got 10 in 1st and 12 in 2nd and 13 in third and 15 in 4th and 17 in 5th.

Snafu
12-19-2004, 05:27 AM
Was it doing this before too? or has it just become a problem recently?

Dumb question, but is your airfilter doing alright?
???

Luni
12-19-2004, 05:34 AM
Oh I would also like to note and add that that FMIC and the piping to it contributes to about a psi or 2 pressure drop across it, so in 1st where I might make 9 or 10 you might only get 7-8.

Lagos
12-19-2004, 06:23 AM
snafu, it has always been like this. airfilter is brand new.

luni, what mods did u have to your motor when u were getting that much boost in 1st?

Luni
12-19-2004, 04:24 PM
Lagos I had nothing done.

Just gutted primary, removed secondary (so basically straight pipe - on stock exhaust). MBC and my fuel cut disabled.

I also have a TRD metal headgasket and thats about it.

Nothin for the most part.

xeril
12-19-2004, 11:13 PM
when my car is actually able to run, it pulls about 5-6psi in 1st gear, and around 12-13psi for the rest of the gears..

Todd
12-20-2004, 02:32 AM
i get a "full" 8 psi in 1st. auto tho, so the gear is a little longer.

Nemesis3S-GTE
12-20-2004, 04:01 AM
I have seen at least 5 psi in 1st gear in the red Celica. I've honestly never try too hard to boost when starting, it just spins the tires usually, and if there's actually traction, 1st gear goes so fast that you're shifting before you know what's happening. The All-Trac is a different story altogether. I can see 10 psi in 1st gear all the time.

Lagos
12-20-2004, 04:04 AM
nemesis, what specific mods do the 2 cars have?

JGS3SGE
12-20-2004, 04:24 AM
lets not start blaming the FMIC and pipes, I'm willing to bet the stock IC has more pressure drop... any manifold side exhaust leaks? Tire slippage?
What do you have for exhaust?

Luni
12-20-2004, 04:20 PM
lets not start blaming the FMIC and pipes, I'm willing to bet the stock IC has more pressure drop... any manifold side exhaust leaks? Tire slippage?
What do you have for exhaust?

Are you serious.

Theres like less than a psi of pressure drop on a stock IC.

I can almost guarantee hes seeing 1-2 on his setup. Look at the piping.. Those things dont fill themselves.

ChrisD
12-20-2004, 04:24 PM
Yeah the stock Alltrac IC has been proven to be quite good. Hmm there was a good article about that. I must locate it...

JGS3SGE
12-20-2004, 04:46 PM
DO I need to whip out the rate of flow per second on your average turbo compressor? Lets just say its less than a 1/10 of a sec. from idle to fill a fridge....
I have a similar setup on my car and I have no problem building boost in 1st, 2nd, 3rd, 4th, and 5th.

Next you'll tell me bigger intercoolers cause more pressure drop...
I need a form letter for these message board myths :lol:

ChrisD
12-20-2004, 04:52 PM
No I am talking about a specific article that tested a heap of OEM intercoolers and the alltrac one was included. It fared quite well actually. I wasn't really commenting on lagos' specific setup.

Snafu
12-20-2004, 06:01 PM
Honestly, we can't blame the intercooler or pipes.

Yeah, there's a pressure drop, but Lagos doesn't have a very long intercooler, and I highly doubt there's such a large drop because of this.

What kind of boost controller are you using?

Something electrical or mechanical associated with your turbo is not function correctly, check all connections, settings etc.

Luni
12-20-2004, 06:55 PM
All Im saying is mod for mod he IS going to have more pressure drop than a person running a stock top mount intercooler.

You cannot refute that. So a pound or 2 in variance is NORMAL.

nuclearhappines
12-20-2004, 07:39 PM
you must have a huge boost leak.

if not then check to make sure your exhaust wheel on your turbo is still 100% there

Also make sure youre wastegate arm isn't bent ..etc and that your flapper door is not jammed open....

one of those 3 is your problem. you will hear the first one and see the car running pig rich.... but the other 2 reasons the only symptoms will be your car running slow...and not boosting hard

it's not your FMIC. you should see some boost even in 1st... dragging a 4wd system is ALOT of load....

-nuke

Todd
12-20-2004, 10:08 PM
yea its not the IC.
i have just as much, if not more piping, and a long as intercooler. boost comes on pretty quick i must say.

Luni
12-20-2004, 11:06 PM
I didnt say that it WAS the ic and piping, I was just saying to make sure to compensate for that when comparing values to say a stock alltrac or stock swap, cause they have less pressure drop period.

I do agree that he should see more than 0 psi in 1st gear. He should see at the very least 5-7 psi in 1st gear.

Nemesis3S-GTE
12-20-2004, 11:29 PM
nemesis, what specific mods do the 2 cars have?

Both cars have a MBC, intake (FWD car has the more free flowing one), All-Trac has stock exhaust with gutted primary cat, FWD has 2.5" exhaust back from the primary cat (still functional), the FWD has the JDM CT-26 while the All-Trac's is a USDM one. I think that's all that really matters as far as spool up on my cars is concerned. Oh, yeah, and i tested the All-Trac again, i was getting 8-9 psi in first gear today. I would definately check for boost leaks on your car, also, maybe check to see of the T-VIS is actually working correctly. Maybe that could be affecting the 1st gear boost.

Lagos
12-21-2004, 02:46 AM
thanks for the tips guys, ill look into them all. i think part of the problem is my near stock 2.3in exhaust and the stock primary cat. im sure that if it was more free flowing, the spooling would be faster. im also going to try to disable the t-vis system and see if that helps.

here are the cars engine mods.

2nd Gen jdm 3sgte swap
Spearco 23x6x3 front mount intercooler
2.25 stainless steal mandrel bend intercooler piping
Exhaust Heat wrap on intercooler piping
HKS SSVQ Blow off valve
K&N Cone filter intake
Greddy SP Exhaust
2.5in mid pipe
twosRus mbc @ 10psi

nuclearhappines
12-21-2004, 03:03 AM
oh ...bov ...

hrm ...is your BOV adjustable ? make sure that's not leaking too...

2.3" isn't that bad an exhaust for the power you're making...

-nuke

Lagos
12-21-2004, 03:09 AM
hahaa nuke, how did u know.

yes the bov was leaking. i have recenty disconned it (vac line caped) and the car pulls much better.

maby part of the problem is my driving style. i know i have never redlined in 1st gear. i probably take it up to 4k, but you figure that should still be enough to make some boost.

Snafu
12-21-2004, 03:21 AM
Wow, you have one of the sweetest cars on the forum and you don't take it past 4k in first? Wow.... I'd be boosting the hell out of it.

Luni
12-21-2004, 04:53 AM
I can almost guarantee you disabling your tvis system is NOT going to assist you. Your car makes more torque at lower RPMs with it, that assists in the spooling of your turbo. More power being made means more fuel being burned, which is more raw energy for the turbo to harness.

Give it a shot but I woudlnt disable it.

Instead Id plug the wastegate actuator, plug the TVSV, and have NO boost control and see what that bitch does then. At least for a test.