I went over to this dyno place yesterday in Topeka, KS to tune the car a bit to make it deliver better power. As good news, I ended up coming with 60hp more than I started with. I initially was making only 275hp and 263 lb/ft tq at 17 psi, and left with 330hp and 326 lb/ft tq at the same boost level after screwing around with the iginition timing.

Anyhow, I think I had nothing but issues with the GT2871R's internal wastegate. After I was done tuning the car, I wanted to see how much power the car would deliver at 20 psi. My only problem while trying to do that was the turbo just wouldn't hold at 20 psi at all. On initial full boost at around 4000 rpm, I'd see the gauge go to 20 psi, but immediately the boost would roll back to 17 psi. I figured the problem was the wastegate being unable to hold that pressure. I just find it weird that the turbo wasn't holding up there as I've seen other people being able to make power at that boost range without any reported issues.

So my question is, am I the only one dealing with the internal wastegate not holding up, or are there others here with the same issues? If so, I'm thinking of saying, "screw it", and will upgrade to a GT3071R and weld on an external wastegate on the T2 manifold so I can make reliable power without anything letting boost leak out like my current setup is doing. It's just very annoying knowing I can make more power, but can't get there for some odd reason.

what kind of boost controller are you using? Also you do not need to upgrade to eliminate the internal gate. Many people weld the internal gate shut and then just use an external gate.

I am using the Greddy Profec-b II unit. It has worked great so far, although I will admit that I don't really know how to work with it, other than taking up the perctange base higher to make more boost. To make 20 psi, I had it set to 64% for high boost, but like I said, the boost falls off immediately from 20psi to 17 psi. I feel that 3psi difference is where I still have lots more power that I can make out of my current turbo.

I know I don't need to upgrade, and I know about welding the internal gate shut, which is why I was talking about welding on an external gate on the manifold I already have (I though I kind of implied it). What I was getting to with that comment was that I'm going to try and use a better wastegate which will be able to hold boost more reliably than the one I already have. And while I'm at it, I'd rather go with a bigger turbo that would make a lot more power with the same lag characteristics, which would be the GT3071R (at least from what I understand, it behaves the same as the GT2871R but has lots more room for power).

I can't help with the question about the wastegate holding or not, but the SpecII can be tricky to tune.

Have you read this?
http://www.sr20forum.com/turbo-guides/86098-how-how-tune-your-greddy-profec-b-spec-ii.html

C

What are your current settings on the Profec Harris?

Interesting read, Chris. It's been a while since I went in to the Technical Information Library. Maybe I need to dig a little more in there and find fixes to other things I've had a hard time with.

Richard, what setttings are we talking about? Call me up if you can so I can discuss this with you in detail over the phone.

OK, I've tried everything I could, and the boost still won't hold. The boost controller last showed a peak boost of 19.8 psi, while my gauge would show that the boost would go that high, and immediately after that, the boost would fall off to about 16-17 psi. I just can't get it to go to a boost point and stay there. This is really aggravating to me.

Someone, please help me out here!

the only electronic boost controller i have experience with is the avc-r and that has a learning mode on it so if the boost levels do not match on the whole rpm range it can self adjust the duty in order to correct it to the boost level you want. It may be an issue with your internal gate though and not your boost controller. Get on the phone or email with garrett and ask them if they have seen this issue with other people running their ball bearing turbos with internal gates. If they say that people are able to run a 20psi level with consistancy on their gates then maybe you should mess with the boost controller.

Have you tried removing the boost controller? I would remove it from the equation and see if it holds steady pressure. Also does the 2871 have an adustable gate like the RS? If so tighten it up and see what she holds.

This will at least tell you if it s the controller.

Wes, that's one more thing I will do. I am going to shut off the controller and see how the wastegate performs with no boost controller involved. I've been playing around with all the settings, but the car just won't hold the same boost all the time, period. Boost even varies in every gear, making it all the more aggravating!

Now, I talked to 91b13det, and he came up with other ideas that could be contributing to boost issues. I am currently using a Turbonetics BOV that probably is past seeing its better days. I was thinking of replacing it with an HKS SSQV, which I understand can hold boost really well in comparison to the unit I currently have. I'm going to start with that as well as screwing around with the boost controller a bit more.

The plans for going with the GT3071R are still solid as I believe the GT2871R will not reliably take me to the 400+ whp level I'm aiming to get to. At least that's what I see from what I'm currently experiencing. While I upgrade, I will also go with an external wastegate in the manner I see some other guys here have done, i.e. mount a TiAl 38mm piece on the stock manifold. Just throwing my not-so-far-away plans out there.

Try doing a run w/o your exhaust system. I heve personally experinced restrictive exhaust leading to less boost also you can try making a run w/o your air cleaner attached. Side note on most digital boost controllers there is a setting called "gain" make sure the "gain" setting is adjusted properly.

What wastegate are you running? I had a 2871r a while back and was able to run 20 psi with the internal gate. I was using the hks evc 4 boost controller though and an hks silvia 1 bar internal actuator.

What wastegate are you running? I had a 2871r a while back and was able to run 20 psi with the internal gate. I was using the hks evc 4 boost controller though and an hks silvia 1 bar internal actuator.

that's what i'm thinking, possibly a problem with your actuator?

I am not sure if it's a problem with the actuator. The wastegate is whatever you get from http://www.atpturbo.com. It is adjustable, and I've tried to screw around with it, but to no avail. Right now, I haven't run it on high boost much since I made this thread, as I just rebuilt my motor. However, I will be testing the turbo's boost capability again and I'll see what it does this time around.

this might be off topic but what is your setup like? those look like good numbers for the 2871

Did you get a solid reading off the dyno for your boost levels??? Also i would never trust a boost gauge for readings, well depending on which one you have..... get it back to the dyno just to get an accurate reading on how your boost is falling off. I also had a 2871(internally gated) and profec b controller and it had some of the same gremlins you have with boost. I just have not had good experiences with that boost controller and i have some decent experience with them. I switched to one of my shops generic manual controller and have had no issues since....just my .02

Bov and cheak for leaks... 1 question do you still have the gti-r j pipe?

GT2876RBLUBIRD - That power I made was on a rather bone-stock blacktop S13 SR20DET. Only mods it had were HKS Step 1 cams, 3" turbo-back exhaust, 850cc injectors, Turbonetics BOV, Z32 MAF and Enthalpy-tune ECU.

My current setup now is the same SR20DET with the following:

- 87mm 300ZX TT pistons
- Cometic 87mm headgasket
- HKS Step 1 cams
- O2 induction intake manifold
- Q45 throttle body
- TurboXS RFL Bov
- Z32 MAF
- 850cc injectors
- Enthalpy-tune ECU

Now the car needs to be tuned on the dyno, but I'm waiting on a friend to send me an E-manage sometime soon so I can correct any issues that I will find once the car gets on the roller.

jp - I don't have a FWD SR20. I now own an S13 with a blacktop S13 SR20DET, so the j-pipe is a non-issue in my case.

To add more to this topic, I did hit full boost at about 18 psi today. Boost went up and stayed pegged at 18 psi for as long as I could keep my eye on the gauge, but I am not sure if the boost stayed at the same level throughout the rpm range. I will check for this tomorrow. However, another problem from the wastegate has arisen. Now, at low boost, if I shift, I can hear the wastegate making a lot more noise than it usually did. At times, it is pretty loud. In boost conditions 10 psi or higher, the BOV opens up at the appropriate time and lets the excess boost off. The loud noise from the wastegate is prevalent even when the BOV is set to the softest limit, so I know the BOV isn't it.

Now, about vacuum, I wonder if that is it. I've made sure all my vac lines are good, and even with that, the best I usually see is about 12 in Hg of vacuum. If it does sit at around the desirable 17-18 in HG, the idle rpm is usually high at around 1800 rpm before the motor settles to 1100 rpm and take the vac down to 12 in Hg.

I would really appreciate it if you guys could give me some guidance with these issues that I'm dealing with. Thank you all.

when you put your % up on the boost.
put warning at 21 psi
set gain at 17psi
put your set back to 30%
do a couple runs and see what it does, higher the set % as you go and maybe that'll work. i have the same thing and its a pain in the ass to actually have to tune it to get the boost you want

Harris, Sorry in advance for thread jacking but what c/r are you getting with those 300zx tt pistions?