Boosting high with T25 after Greddy BOV installation

PokeyTheDSM · Jul 20, 2002

Before you ask, yes, I have checked all boost leaks, replaced the silicone lines that had rotted away, but my T25 seems to be running really high boost.

I put the greddy BOV on, I tried running the line from between the turbo wastegate and the actuator that leads up to the second nipple, and I was hitting upwars of 2.0 bar! (momentarily)) so I tossed that out and put the straight line back in (Someone should update the VFAQ that you should run a Boost Controller before you do that).

Now it's running still very high. I've hit 1.5 (around 21-22 psi) bar a few times in second and then it drops, but when I'm in third, it stays at about 1.2-1.3 (17 psi!?!?) bar which seems VERY high. I didn't run the car that long in third to see if it dropped a lot or at all, so I'm hoping this is okay. I'm still runnign the bone stock fuel system, and would rather not have my one method of transportation blow some pistons.

Few facts: I am running an N1 Downpipe (I know it was supposed to spike, but this much? And for this long?), 94 Octane, Venting back into the intake. My exhaust temps are normal and are not going over their regular tempurature. The little wastegate solinoid restrictor is long gone due to a previous owner.

I'd appreciate it if this is considered normal, or if I've screwed up somehow. It seems just to be boosting too high and going too fast for a simple Upper intercooler pipe/BOV upgrade.... or are 2nd gen BOV's that much of a giant plastic piece of shit?

whitegst97 · Jul 20, 2002

By any chance, caus ei jsut read over your prob quickly, you have a boost a controller i assume? If you have the factory boost controller and an aftermarket boost controller, even if your boost conrtoller is fully close you will be boosting very high. So check if you still have the factory BC.

itdood · Jul 21, 2002

I just put on a joe P MBC on my t25. Ran it with the stock BOV for a few weeks. One day, one of the MBC hoses came off and and I boosted to about 22 PSI before fuel cut safed my ass....

Judging from the levels you are hitting, it doesn't even sound like there is any boost control. Try running a hose from the turbo outlet nipple to your waste gate actuator. That will just keep the waste gate open and should keep boost down around 11 or 12 PSI.

From what I read though, it sound like your problem is lack of boost control. do you run an MBC? have any of the hoses popped off?

AWD Terror · Jul 21, 2002

You didn't mention it so I'm going to assume you don't have an MBC? With the mods you've described (Greddy BOV, IC pipes and downpipe) you're going to NEED one to keep boost under control.

Another thought - if you've just got the downpipe, but no cat-back exhaust then you're likely seeing serious boost creep too.

Pizzy · Jul 30, 2002

overboosting

I'm boosting rather high for my mods too, w/o a bc of any sort (aside from factory bcs). The only things I've heard from other dsm'ers that would help my problem is to have the wastegate ported. I'm not sure exactly how to go about this but if you boosting out of control kinda like me, maybe that's something you should look into as well.

AWD Terror - I thought boost controllers couldn't lower boost? I thought that an ebc would be capable but someone told me it's not. A mbc on it's lowest setting would only give him the same levels of boost he's already at right? Seems like they only work to turn boost up from where your current boost levels are. And if it's turned up, then it gives you the ability to turn boost down, but once again only to the levels you were boosting at before the controller was on there.

This is just what I've gathered in my search to regulate my boost. Like Pokey, I've got too much boost and no one seems to have a way of turning it down aside from the wastegate solution (or using more restrictive intake piping). If I'm wrong, sorry, but it's the best of my understanding.

PokeyTheDSM · Jul 30, 2002

Get a ported O2 housing and hope for the gods of the T25 not to let it spike. Also make sure the restrictor in the stock BCS is still in... I didn't have mine in (the car had it missing all the time), and that's why I think my turbo decided to go south for the winter from the spikes.

Sigh sigh... Three to four week wait on a bigT28? God damn it...

-pokey (who has no car to drive anymore until his turbo is fixed)

Pizzy · Jul 30, 2002

HALELUIAH!

I guess I did something right cuz the ported o2 I bought should be in the mail and at my door in a day or two!

So having the ported o2 on there will help against boost creep? I thought the wastegate being ported was what would defend against creeping? That or an external, but damn those are BANK.

So why would the ported o2 help against boost creep? If anything I would think it'd increase the problem with quicker spoolups.

PS - I bought it with the notion of putting it on AFTER I got my boost problems fixed, because of the quicker spoolup. But hell if it's going to lower my creep, I'm glad it's on its way.

Damn I hate being a newbie...

whitegst97 · Jul 30, 2002

maybe i read wrong i have a feeling i did, but do you still have the factory bost controller and an aftermarket boost controller??

Pizzy · Jul 31, 2002

when i bought my car it was used, but to the best of my knowledge the bcs is still there. and there is no aftermarket controller on there...im just boosting at ridiculous levels with the mods in my sig, i cant figure it out...need a way to turn boost down and apparently no boost controller will lower boost levels below what they are without a controller there (ie - what im currently at). porting the wastegate or getting an external will help i've been told, but idunno y a ported o2 would help.

Thanks for your time guys.

itdood · Jul 31, 2002

Pizzy said:
when i bought my car it was used, but to the best of my knowledge the bcs is still there. and there is no aftermarket controller on there...im just boosting at ridiculous levels with the mods in my sig, i cant figure it out...need a way to turn boost down and apparently no boost controller will lower boost levels below what they are without a controller there (ie - what im currently at). porting the wastegate or getting an external will help i've been told, but idunno y a ported o2 would help.

Thanks for your time guys.

What's the boost hitting?

Looking at your mods, I would be inclined to say you shouldn't have any problems controlling boost. Something is up.

Perhaps there's a major leak in the stock BCS plumbing?

You should run a hose directly from the compressor nipple to the waste gate actuator to test. This would open the WG as soon as boost comes on. It's the same thing as having a MBC or EBC tuned to the lowest boost setting, i.e. wide open. This wold be the MAX that ANY controller can turn down boost.

Be sure to fasten the hose down, it can pop off if you just slip it on. Use cable ties.

If you still get spikes and overboosting, then something else is up. Could even be a stuck WG...

Pizzy · Jul 31, 2002

From http://www.dsmtalk.com/forums/showthread.php?threadid=50827&goto=newpost :

"when i had my car dynoed, the guys let me borrow a mechanical boost gauge for a spin around the block. it showed 12-12.5psi at WOT just like i thought. when i installed my turbo timer, it showed 1.0bar at WOT...but 1bar = 14.5psi...and i think the mechanical gauge would be more accurate than the turbo timer's.

now then:

if 14.5psi = 1bar
then 12.5psi ~ .86bar

so if im at 1.4bar on the turbo timer...

1.4bar * 14.5psi/1bar = 20.3psi according to the turbo timer

BUT...if going off the mechanical gauges reading, of .86bar...

1.4bar * .86 = 1.2bar (that's what im actually at according to the mechanical gauge)

and 1.2bar * 14.5psi/1bar ~ 17.5psi

so either im overboosting at 20.3psi or im sittin a lil high on 17.5psi...anyone wanna help me out on this logic? which am i really running at?"

So that's the story behind what psi I'm at. The guage is in the mail and I'll know for sure what's up with it once I have it installed. I REALLY have to do my homework on how the whole setup between the exhaust manifold to the dp works. Once I think I understand it I find out I don't, and I haven't found any detailed explanations online.

In any case, I know the wastegate being enlarged would help prevent overboosting but I just don't know how to go about it. and getting an o2 eliminator for an external wastegate setup is a lil outta the question...I just got a ported o2 housing and the eliminators are kinda expensive (quickly running low on funds...college student) and I'm not sure about all the different ways to dump. I'm assuming "to the atmosphere" is illegal, plumbing it back to the DP sounds about right, and there was another option I can't remember right now.

If anyone has a good site or something that'll show me in detail how everything comes together it'd really help me out. Thanks.

itdood · Aug 1, 2002

Pizzy said:
From http://www.dsmtalk.com/forums/showthread.php?threadid=50827&goto=newpost :

"when i had my car dynoed, the guys let me borrow a mechanical boost gauge for a spin around the block. it showed 12-12.5psi at WOT just like i thought. when i installed my turbo timer, it showed 1.0bar at WOT...but 1bar = 14.5psi...and i think the mechanical gauge would be more accurate than the turbo timer's.

now then:

if 14.5psi = 1bar
then 12.5psi ~ .86bar

so if im at 1.4bar on the turbo timer...

1.4bar * 14.5psi/1bar = 20.3psi according to the turbo timer

BUT...if going off the mechanical gauges reading, of .86bar...

1.4bar * .86 = 1.2bar (that's what im actually at according to the mechanical gauge)

and 1.2bar * 14.5psi/1bar ~ 17.5psi

so either im overboosting at 20.3psi or im sittin a lil high on 17.5psi...anyone wanna help me out on this logic? which am i really running at?"

I did the math a bit different than you but came up with the same error on the turbo timer, which is 14% according to the mechanical gauge you used. More than likely though, the error in the turbo timer boost gauge is a straight line 14%, it probably scales up as it goes higher. (BTW, you should be flogged for relying on a turbo timer as a boost gauge

)

Just with intake mods on a t25, you can expect to hit fuel cut around 15 or 16 PSI (unless you have fuel mods and an AFC or a defencer), so if you're not feeling that stutter, you probably aren't hitting above that level of boost. If you leave all the stock plumbing alone, you can see up to 19PSI before fuel cut (that's been my experience anyway), because of how restrictive it is. But, open things up with just a nice UICP, and the turbo has more breathing room, you hit fuel cut at a lower PSI. Fuel cut is your safety net here, if you overboost. Fuel cut is 1 of 2 things, it's either when the injectors are at 100% duty cycle or when the MAS flows over a certain amount, I'm not sure which it is because I've seen guys say both of these but I've never gotten any clarification on it. I'm inclined to say it's when the MAS detects too much air flow.

So anyways, are you feeling fuel cut? Was anything done to the car to disable fuel cut (hopefully not at this point)?

You really shouldn't need an external wastegate with a t25 (that's putting it lightly). Even with a big 16 you can still internally gate enough exhaust out. Usually guys I've seen don't start to externally gate until 20g+

From everything I've, I think you are relying on an inaccurate boost gauge to assess things.

I honestly didn't even know that any turbo timers came with a boost gauge. How does it work, where does it pick up a boost signal, how does it send the signal to the timer?

IMHO, (I know you didn't install the thing), turbo timers are a waste of $ and space anyway. Perhaps they're needed on dry turbos (none water cooled). On a wet turbo and normal driving conditions, they do nothing.

talon97tsi · Aug 1, 2002

i'm in your basket. lol waitin on a MBC. I just added my 1G BOV and Buchur UIC that's the full replacement. Anyway i was running 12psi on the 2g BOV i'm now spiking 22psi and it drops to around 15psi. I'm on an automatic and when i WOT has some crazy sounds lol. I don't think i'll do that much while spiking 22. I'm just watching my gauge close until the MBC gets here. BTW at the 22 spike i can spin from 25mph on the FWD lol it's crazy but i rather keep my engine than be a dumbass.

Pizzy · Aug 1, 2002

itdood said:
I did the math a bit different than you but came up with the same error on the turbo timer, which is 14% according to the mechanical gauge you used. More than likely though, the error in the turbo timer boost gauge is a straight line 14%, it probably scales up as it goes higher. (BTW, you should be flogged for relying on a turbo timer as a boost gauge )

Hehehe, yeah I wasn't really RELYING on it, just using it to guesstimate until I decided on what gauge I wanted to get. Oh, and you got 14% because you just worked it the other way around...100% - 14% = 86% (.86 bar remember

)

IMHO, (I know you didn't install the thing), turbo timers are a waste of $ and space anyway. Perhaps they're needed on dry turbos (none water cooled). On a wet turbo and normal driving conditions, they do nothing.

Actually, I did install it myself (pretty flawlessly I might add) and it takes the boost signal from the line off the throttle body...the same area that most people tap for their boost gauges. To me it's not a real waste cuz I've had a lot of people here tell me about how they've damaged their turbos becuz they just turned the car right off after racing and heavy spooling. Rather be a worry wart and have a fuctioning turbo than to say "hell with it" and then not be able to race.

Pizzy · Aug 1, 2002

talon97tsi said:
i'm in your basket. lol waitin on a MBC. I just added my 1G BOV and Buchur UIC that's the full replacement. Anyway i was running 12psi on the 2g BOV i'm now spiking 22psi and it drops to around 15psi. I'm on an automatic and when i WOT has some crazy sounds lol. I don't think i'll do that much while spiking 22. I'm just watching my gauge close until the MBC gets here. BTW at the 22 spike i can spin from 25mph on the FWD lol it's crazy but i rather keep my engine than be a dumbass.

See here's the thing though, an MBC may help prevent spiking (idunno) but it can't turn boost levels down. Same with an EBC I suppose. That's basically what I was lookin to do and apparently porting the wastegate is my best option.

Also, even before the Brode UIP and 1G bov, if I went WOT at any point before 4000rpm in 1st gear, I was spinnin for sure! Now if I'm anywhere before 5000rpm, I'm spinnin at WOT. and second gear doesn't burn, but she can chirp the hell out of it (manual tranny btw).

BTW: I have an extra intake manifold ported to match a 1G TB ('92 style, soon to be at my doorstep), a better lower intercooler pipe, a high flow cat and ported o2 housing that are waiting to be installed, along with a soon to arrive AFC. I'm planning on getting a 2.5" dp so I'm probably not going to install the exhaust stuff until I can slap em all on together, and I'm not sure I want to add much more free flowing air components (except the LICP) until I get my EGT (in the mail) installed to tell if I should add bigger injectors (and maybe a better fpr and/or rail). Yes I know I still only have a t25 w/ the stock sidemount ic, but I'll eventually have enough money to get to those too and I'd like tem to be well supported.

In any case, some suggestions as to what order I ought to do these mods would be appreciated. If it means waiting for a DP to get started modding, I'm happy with my car's performance so far so waiting won't matter. Thanks.

talon97tsi · Aug 1, 2002

yeh surprisingly if i drive it well enough now i can actually spin some of second on my auto tranny. OH and yeh i have the translab in with black spring so that helps keep the power when it shifts, anyway from the way you sound could i borrow a lil money lol I'm on my 3rd block right now i'm finishing additions to the car itself and flow but i'm gonna rebuild one of the other blocks from the ground up. My senior year project. Anyway yes i'm 17 yrs old lol but i do pay for most of the shit myself and have done all of my own work on the engines. I don't understand what you mean by it can't lower boost. The MBC should control or help control when the BOV opens. that being the reason you should be able to set it at 16psi and it not go over unless you have a major spiking problem. I"m not sure but i don't see how the t-25 can have too much of a spike on it. i wouldn't run more than 15-16 psi as a daily thing on a t-25 i'm about to do my fuel pump rewire o the fun. um yeh well i'm gonna stop rambling now.

AWDx4G63 · Jul 10, 2004

Hi guys,

Sorry about digging up this old post. My question is indeed belonging to help forum.

I incorrectly installed an MBC that is borrowed from a friend onto my 2G GSX. Purpose of that was to decrease boost of 15 psi to 12 psi (like stock). This heightened psi was the result of putting UICP and HKS BOV. So I didn't read anything about installation, then plug into the MBC between nipple from T-25 compressor outlet and actuator. WRONG WRONG WRONG.

I took the car out to drive and boost spiked to 25 psi for less than a second. Is that ok? My car seems perfectly normal. Very serious, it's only at 3000 rpm for less than a second. I hope I didn't damage anything. Then I thought I need to turn the screw in more, but it didn't do anything, and it spike to a 20 psi before I let go. also less than a second. so I only spiked twice for less than a second... I don't know why fuel cut didn't come in to rescue me. Is that ok? Is my car alright?

by the way,

I have stock fuel component, t-25...... only has air filter and UICP

Thanks, any response is appreciated

I'll correctly install MBC tomorrow.
Andrew

Pizzy · Aug 31, 2004

UBER-Late reply, but check that the hose is the same size as stock. I put a hose on that was too big and was boosting up around 25psi by accident as well a LONG time ago. Fixed it by getting smaller hose for the BC.

Yeah I'm sure your car is fine though.

AWDx4G63 · Aug 31, 2004

Thanks, Pizzy.

I has been 2 months since I overboosted. My car did seem to be perfectly fine. Thanks.

I figured out I installed MBC incorrectly. Then I used JoeP BMC installation instruction from vfaq.com, it fixed it.

4G63 is too strong... haha.

thanks,

Andrew

Boosting high with T25 after Greddy BOV installation

PokeyTheDSM

whitegst97

itdood

AWD Terror

Pizzy

PokeyTheDSM

Pizzy

whitegst97

Pizzy

itdood

Pizzy

itdood

talon97tsi

Pizzy

Pizzy

talon97tsi

AWDx4G63

Pizzy

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