GT2871R/redtop SR questions. YES I searched lol

[copmagnet]

Ok here go a few questions. I've searched a lot of stuff but not managed to find the answers I was looking for.

Ok, I have a redtop swapped 91 coupe. FMIC, GT2871R turbo, .86 exhaust side and 740cc injectors with an Enthalpy ecu. I HATE THE LAG!!!! Its horrible, this is a street car, I want more response. I got an insanely good deal on the turbo, so couldn't pass it up, but didn't realize just how bad the lag was going to be compared to stock. I don't hit full boost til past 4k RPM's. Sure, it could be a lot worse, but thats enough for me to nearly go back to a T25. Time for the questions: the wastegate I am running is a stock internal one, 8psi or so. It has what looks to me to be an adjustable arm (bent one, not straight). When I installed it, all I did was snugged it up so when closed the arm was as tight as possible. Is that correct? Would an aftermarket 14psi or so wastegate help the turbo spool faster, due to it not starting to open til much later? BTW I am running an HKS EVC EZ, its electronic, but basically just adjusts max boost, no tuning options.

Second question: I am thinking of just buying a .64 housing and swapping that out, just how much sooner would that pull in my boost? Hate to spend that kind of money and time for something that might not get me where I want. part 2: can i use different exhaust housings? Would an S14 or S15 T28 housing bolt on to the 2871R and do the same thing? Close? Or not possible at all?

Question 3 pertains to cams. Not 100% sure I want to swap them, since I know cams will move the powerband up higher. I know engines, but I am much more experienced in the old V8's. Keep in mind, this is a daily driver, i don't drift, I occasionally hit the drag strip and am planning on attending some track days here and there for fun. But primary purpose of this car is street driving. I've read so many conflicting things so many places, would a 264 shove my powerband too much farther up for a street car? Go with a 256? Or is a 256 such a small increase it won't be worth the trouble/expense? I plan on pulling the head soon to install ARP studs and a new gasket/valve seals, so I can do cams then if its worth the trouble. Hell, i remember running a 300 or so duration .525 lift cam in an old V8 i built 15 years ago, power came in real late, but a V8 had enough grunt that it still pulled hard even out of its optimum powerband. this 4 cylinder turbo stuff is kinda new to me.

I just like being able to hammer down and start getting boost ASAP when I feel spunky, this wait for boost shit is killing me.

Any help will be greatly appreciated guys!

[NiSilS14]

A aftermarket actuator isn't going to give you a sooner threshold on your turbo I'm not sure how the HKS evc is, but is there a "gain" feature on it? Sometimes adjusting the gain can affect the spool time of the turbo. A different housing will have a dramatic effect on changing the threshold of turbo. Between .64 and the .86, I would guess it would be about a 500-800 rpm difference. Try finding other people's dyno and compare those. Stock turbine housings won't fit, the turbine wheels are sized differently. IMO, cams is one of those things that could help given that you find a way to tune for them. Tuning will aldo play a huge part in how a turbo will behave. IMO, It's necessary when swapping exhaust housings, cams, intake, etc..

[copmagnet]

Right, once I got everything on I was going to take it to a local shop and have it tuned on a dyno. Which brings me to another question, I was thinking of buying NISTUNE, but since I have a tuned ecu with a chip in it already, can that be retuned by someone local, or is it proprietary to Enthalpy? If it is an option what kind of software etc would he need, so I can make sure to find a tuner who can do it? I would prefer having it tuned on a dyno to my exact setup over mailing it off for another off-the-shelf tune. Kinda wish I had gotten nistune in the first place, but the car was down and I needed it running asap. This ecu was there and plug n play so I could drive it.

[SLiDe_WaYz]

You didn't see the 40 page discussion on 2871r users? I'm sure all your questions have been answered in that thread it includes dyno charts as well as mods list.

[copmagnet]

I saw that, and read a lot of it, but good god almighty there are over a thousand posts, and after the first few hundred I was lost as hell from all the back and forth debating. Then the cam thread I read was long, very detailed, and left me still wondering just exactly I had just read lol. I understand the basics of engines, cams, boost, things like that. But the questions I have are more about powerband than anything, and I hadn't found the answer I was looking for just yet. I want usable power on the street. What about a 256 intake cam and 264 exhaust? I've seen people do that. What is the benefit of that? I'm not looking for a 9 second street car, i just like it to GO when I hit the gas, not creep until I finally get my turbo spooled. Hell with the old T25 I could floor it on the highway and have instant boost, now I have to downshift if I need to pass. THATS what I want.

[fliprayzin240sx]

What are you using for tuning? Even with a .86 AR, it shouldnt be that laggy since its still a small turbo.

[copmagnet]

Its got an enthalpy tuned ecu in it now. I think I'm just going to order a .64 housing this weekend, pop that on with an HKS wastegate just cause, and see whats up then. I'll worry about cams later this summer when I decide when to pull the head for a new gasket and studs.

Now as for cams, I've seen some people running the 256 intakes and 264 exhaust cams. Why? I know on old Chevy small blocks, I ran a dual pattern cam because Chevy exhaust ports sucked balls and it needed the added lift/duration to scavenge the cylinders. But what about the SR20? Whats the benefit?

[TheRealSy90]

Greddy intake manifold, Jim Wolf S4 266 duration .464" lift cams, ported head.

Problem solved.

[copmagnet]

I would consider that, but how is the powerband? Thats my main concern. Wouldn't the larger plenum/shorter runners on that intake kill some bottom end for the sake of top end power? And I hear conflicting stories on 264 cams. Some say perfect for street, some say they're not suited as well for it. I might just have to say F it and do it, see what happens.

[JDMRIDDAZ]

that turbo shouldnt be laggy on ur setup
it seems like the tune or sumthing
my boy has that turbo w 750cc inj ebay intake ebay ex mani
w enthalpy tune and a ebay boost controller with no lag issues
does the turbo have in and out shaftplay

[copmagnet]

No shaft play at all, it was new. Stock intake mani, stock exhaust mani. 3" from the turbo back. 2 1/2" hotpipe and 3" coldpipe on the intercooler. I guess it all comes down to what you consider lag too, if I'm on the highway in 5th and I nail it, I don't pull full boost til like 41-4200 rpm's. And that takes a bit. I have to downshift if I want to go anywhere fast. I liked the T25 when on the highway, I could hit it in 5th and have instant power. I'm ordering a .64 housing this weekend. Hopefully thats all it is. I'm going to have to do a lot of reading on cams, can't find much info other than spending a month trying to decipher that huge 2871R users thread. And hope someone in there is running the same setup and their dyno sheet is still there. A lot of the older posts I see in there the pictures are gone.

[codyace]

Have you set timing properly?

I hate to assume, but I think much of your issues come from your background...there isn't a turbo 4 cylinder that is going to have the grunt and produce the power you'll be looking for. I could be wrong, but it may be the deal. It's obviously a natural problem with any turbo car that makes big power.

A .64 housing turbo with any of the 256-264 duration cams should easily make 20 psi before 4000 rpm (unsure on the .86 but it is a little later in power than the .64).

(I personally suggest JWT S3 cams)

[copmagnet]

The S3's is what i was looking at. I did see that in a lot of your posts in the 2871r thread. I was actually perfectly happy with the powerband of the T25. The only reason I went to a 2871R is the old turbo oil seals went bad, and I got a new GT2871R for 500 bucks with a spare exhaust housing (which i just sold for 200). Now I just want to shift the powerband back down. Thanks for the input! And yes I checked timing also, its dead on. I've downloaded the FSM, and went from there. I dyno'd 237whp and 270 or so torque last spring on the T25. I'd be happy as hell with only 325 on the new turbo, as long as the power was where i wanted it. Of course, more is better lol.

[codyace]

If you're only looking for 300/325 hp, then you may be better looking into a 28r as it would spool nice and quick, yet still has some top end to work too. Trust me when I say, a 28r car would be plenty fun :D

[copmagnet]

Right but i already have the 2871R and its already installed. Like I said, I'd be happy with 325 but more is better lol. I just want whatever I end up with to be responsive. I've been trying to dig through that 2871R thread, but its long as hell and some of it just leaves me with more questions lol. So....Stock bottom end redtop, I'm putting headstuds and a new headgasket on it, stock intake mani and exhaust mani, bottom mount 2871R with the .64 housing on 14 psi for street maybe 18 for fun. That should hopefully get me responsive enough power, would the S3 cams still keep me where I can have full spool in maybe the 3500-3600 rpm range? If so i guess that'll be the plan. And it'll basically be done, this is a driver after all I'm not going too crazy on it.