Max boost question

[Bluefire16]

Ok, so the car is almost stock. Stock t25, with a mbc, greddy type s bov and new pipes. So heres the thing, car boosted 12 pounds fine with the stock boost controller on, i got my MBC and installed it, pulled about 18 psi. So i turn it down a LOT! It then goes to 10, alright so i got it under controll, slowly put it up a pound at a time. I boost fine to 12 pounds, so i decide to goto 13, but the car stays at 12. Ive done 2 boost leak teasts, and NONE. When WOT in 4th it goes to 13psi but not when WOT from 1-3? It only goes to about 10-11....

 

[97 4G63]

That's weird your t25 should run at 14psi stock.
So you still have a boost leak somewhere.

 

[grantman10]

Thats funky. What kind of boost controller do you have?

 

[Aphix]

Your wastegate is set up at 10 psi, you may have turned the mbc screw the wrong way?

 

[grantman10]

The weird thing is that he is getting more boost in 4th than 1st-3rd. Usually it is the other way around because of boost creep or boost spike.

A good thing to live by with DSMs is whenever something is being funky do a boost leak test, again. What PSI are you testing to, and how long does it hold?

 

[Aphix]

Yeah, does it spike 13 psi or hold 13 psi?

 

[Bluefire16]

Ive checked it twice and cant find one anywhere..... im gonna try and use a bike pump (### my air tank is kinda loud and try the soapy water trick) but stick any other ideas? But why would it go to 13 only in 4th?

Yea it goes to 13 and sticks solid forever.....but when in going from 1-3 gears its wobbles from 10-11 and doesnt even spike any higher.

 

[Aphix]

Hmm, I find that odd because mines at 15 psi and at WOT in 4th gear (A/T), it lets off to 13 psi, but I was told this is common. I think the fact that it wobbles may be a leak too, you should check your BOV and vacuum line to make sure you aren't leaking boost.

 

[Bluefire16]

...haha ok thats alright you find it odd but its whats happening, hey tomorrow on my way to school ill make a video of it and post it. And snap a couple pics to show i have all the lines hookd up right. (What about the fuel pressure solenoid? I have it unplugged and it just goes from the intake to the boost gauge to the fuel pressure regulator.

 

[All_Boost16G]

I had almost the same problem. Mine would only go up to 10 psi and lower in some gears, with a MBC. I tired everything boost leak checked, and switched out wastegates. I have about 3 MBCs trying them. No matter waht way I turned the MBC it would go down, or stay the same. Until, I switched out BOV, I was using a stock 1g BOV, I guess something was wrong interally, never really investaged.

 

[Bluefire16]

So your problem was the BOV? Hmm i was think to loosen it a little and see if that helped...

Ok so here are a couple pics and videos of whats going on...i have one of the engine bay and a pic of the boost controller... If the videos dont work click the link next to em.

<img src="http://img362.imageshack.us/img362/2096/cimg0261np0.jpg" alt="Image Hosted by ImageShack.us"/><br/>By <a target="_new" href="http://profile.imageshack.us/user/grussell16">grussell16</a>, shot with <a target="_new" href="http://profile.imageshack.us/camerabuy.php?model=EX-Z77&make=CASIO+COMPUTER+CO.%2CLTD">EX-Z77</a> at 2008-10-01

<img src="http://img205.imageshack.us/img205/945/cimg0272nd2.jpg" alt="Image Hosted by ImageShack.us"/><br/>By <a target="_new" href="http://profile.imageshack.us/user/grussell16">grussell16</a> at 2008-10-01

HERE IS THE VIDEO FROM A DIG: <embed src="http://videos.streetfire.net/vidiac.swf" FlashVars="327e3904-d1f3-440a-89a9-9b280166726a" quality="high" bgcolor="#ffffff" width="428" height="352" name="ePlayer" align="middle" allowScriptAccess="sameDomain" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer"></embed><br /><a href="http://videos.streetfire.net/video/From-a-dig_188399.htm?ref="5bc4d2cb-7f67-4717-851e-9b2801658093">From a dig</a>

Heres the 4th GEAR PULL goes to 13: <embed src="http://videos.streetfire.net/vidiac.swf" FlashVars="89c627f2-cd7d-4bb5-8df4-9b28016782e3" quality="high" bgcolor="#ffffff" width="428" height="352" name="ePlayer" align="middle" allowScriptAccess="sameDomain" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer"></embed><br /><a href="http://videos.streetfire.net/video/13-pounds-4th-gear_188401.htm?ref="5bc4d2cb-7f67-4717-851e-9b2801658093">13 pounds 4th gear</a>

 

[All_Boost16G]

First thing i would maybe try is to tighten up your BOV slightly, and remeber to loosen the nut, dont try to just tighten it with a allen wrech, beacuse you will have a major headache if it strips. But what might be happening is that your BOV is keeping closed and the valve is actully prematurely open slightly, which would cause it to only hold 10psi. I would try about a 1/2 a turn to a turn and that should fix it.

 

[Bluefire16]

Ok guys, so i did ANOTHER BOOST leak test, still found nothing. Used soapy water and everything, so i decided to connect the wastegate right to the turbo (this would be the ultimate test i thought) SURE enough, holds 9psi beautifully. So no leaks. Hits 10 settles to 9 and just holds, but when i finally get into 4th it goes to 11 and holds? i figure higher rpms thats why? So what now could be the issue?

 

[the_mork]

Its hard to tell if your mbc is on correctly since I can't quite see where the lines are actually ending and they are very close on a t25 but the line that goes to the right in the picture should go to the wastegate. If thats the way you have it then if not then turn it around. I'm not seeing anything else that looks like a problem but you might want to check your turbo for shaft play, just pull your intake tube off and grab the shaft on the inside of the turbo by the nut and wiggle it, a little side to side play is okay as long as it can't contact the housing but in and out play is bad, obviously don't do this while its hot. Lastly have you tried cranking the mbc all the way tight or are you just going in little increments? MBCs tend to not have a linear relationship to boost.

 

[LandoAWD]

Crappy spring/ball in the MBC? Have any turbo'd friends you could borrow a known-good one from?

 

[viperlp01]

Ya mine did the same thing so what i did was got a different boost source. I just kinda plugged the sourse from the turbo and used the bov line to control boost when i was running the t-25 and that worked way better. I always held on exactly what i wanted. Im not sure if the volume changes or something when i was in forth but that 4th pull sometimes went to like 18lbs when pulling on the free way. I had it rock steady on 15-16 on 1-3rd. Try that and let us know. P.s. If your ever around kzoo there is alot of guys that can help you out on this issue. I made a few MBC's that work awesome so if you want to try a new one i can let you try one.

 

[Bluefire16]

Thanks guys, a friend things my car is backing off since its an automatic and is keeping it from detonating. And autos only have 390cc injecorts....so im putting in a 14b and 450ccs in a couple weeks (just ordered the turbo and injectors for only 100 bucks!) So im not to worried but yea im gonna put the boost controller back on and ill let you know ( OH and i did have it connected correctly, fyi) THANKS THO!

 

[the_mork]

Your friend is kind of an idiot.

Your car has 450cc injectors, only the automatic 1gs came with the smaller 390s. Automatic also has nothing to do with a timing retard which would happen on a manual transmission as well and timing retard will have nothing to do with the amount of boost you can run (at least in your case, some extreme cases might matter but thats not even related). A 14b is a good upgrade but you might want to keep all of your variables static and just change one thing at a time until you get this figure out, just throwing parts at something will usually just hide a problem and get in the way of solving it.

I would try what Lando suggested and see if a different mbc might help.

I don't think it would hurt anything to spray a little wd-40 into your mbc but you might want to wait on that until someone that's either done it before or knows it's a bad idea can chime in.

 

[crimsonGST]

Just try a different MBC. I also agree with mork on the new parts.

 

[91tizzy]

why is everyone thinking that more boost in taller gears is abnormal?....more load on motor generally equates to a slight raise in boost pressure. Boost drop off at higher rpms with a smaller turbo is because the supply the smaller turbos can give the motor is overridden by the demand of airflow the motor needs while it approaches redline....basically the pistons are sucking more than the compressor can blow. As far as the op's problem have you taken the boost controller apart to see what the spring and ball look like? Try stretching the spring a little bit to make the ball harder to move thereby delaying the signal to the wastegate.

 

[Bluefire16]

Thanks Tizzy, good info. And yea i have a good amount of friends in the area ( all DSM owners also) that i can borrow there boost gauge from. But thats the sort of info i was looking for, i figured its what should be happening but know one clarified it. Thanks

 

[91tizzy]

Not a problem at all man...just be careful when stretching the spring if you choose to do so....when I tune my car (automatic as well), I usually will leave o/d off of course and do a "kickdown" from about 50mph. Watch the boost gauge with your peripheal vision aka KEEP EYES ON ROAD. Let it go into third at full throttle and it should peak as far as boost is concerned. Thus eliminating the "false" readings that boost spike can give in first gear.

That's weird your t25 should run at 14psi stock.
So you still have a boost leak somewhere.

Wrong info. 9-10 psi is what the stock wastegate springs are set to release at.

 

[Bluefire16]

Alright, Oh but i invested in the Manual Shift Box actually.... so i can shift whenever i want... I LOVE IT! I ordered it off of Tim on here, great product. But anyways, thanks for the info.

 

[91tizzy]

Alright, Oh but i invested in the Manual Shift Box actually.... so i can shift whenever i want... I LOVE IT! I ordered it off of Tim on here, great product. But anyways, thanks for the info.

thats funny I was gonna mention this to you as I have one as well...definately the shit