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Posted by fatso, Aug 14, 2005
Turbo System Tech - 4G63 turbos, Intercooling, Boost Control, Wastegates, etc.
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I live and race in SLC Utah. elevation 4200ft. my best 1/4 mile was a 12.831@110 this was with DSMlink, with a SAFC I was still ran a high 12.8xx but the timing curve is much easier to maintain (I just posted in a previous post of yours). I have never been on a dyno so I can not give HP or TQ numbers but she does move even more so when you look under the hood and turbo is so small you can barely see it with the exhaust mani heatshilds on. Best thing to do is take your car out yourself and run it, you will see what it can do. I hate when I see a freinds car (after they sell it) out and about I ask the new owner "what can it do"? they answer I run xx.xx, I ask when? the say well it wasn't me but I was told it done that before. ALOT of racing is in the driving and your familiarity with your car. 2nd most important thing is TUNING.
I have kind of set up a goal to eventually put down about 360 to the wheels with that turbo and I believe it can be down after i add my imaginary hks cams and magnus intake manifold, coming soon now I am anticipating 330 whp after tuning. sound reasonable?
I wasn't a firm believer of the BIG T28 but after I got my baseline runs in with a mediocre tune, that little bastard does pack a punch. I'd recommend an adjustable actuator, even though I didn't have one, I've heard from reliable sources they work great.
I was under the impression that I could only purchase a 17lb bigger articulator instead of a adj.one for the t-28?
my buddies always saying 16g.. but he has boostcreep issues and it spools kinda slow..
You say your engine is "high compression", but did you build it that way or is it just a stock NA engine? If its a stocker, read thru a few posts in the NA to turbo forum and get a idea of what works and what does not. If it were up to me I would have waited a bit and got a bigger turbo (Full garrett 60 trim) with a bigger exhaust housing. The things are good on pump, better on 110, good at the track and street. "just enough" IMHO.
I'm going to try a boost controller with rpm programmable settings. I've already run 21 psi at redline, but I had to tolerate 24-25 psi in the midrange. Man, the power difference between 21 psi in the midrange and 24-25 psi is huge, at least 30 h.p. So its obvious my wastegate actuator can hold the exhaust back pressure but not in a linear way.
I'd say to run even 330 w.h.p., you'd need to hold 21-23 psi to 7000 rpm to have a chance. On another note, cams are a guaranteed 25 h.p. on a T28, worth every penny.
My goal is to hit 38 lb/min on my T28, highest I've hit so far is 36.5 lb/min.
Those 14b equipped cars were most likely light weight 1gs, possibly even FWD, and gutted to boot, along with high octane race fuel, and a high flowing 1g intake manifold and cylinder head. You can't compare that to a heavy 2g AWD on pump gas. Strap a T28 to that 14b equipped car and it would pick up 5 mph.
I'd expect a full weight 2g AWD on pump gas running a T28 rated at 35 lb/min to trap 111 mph using the trap speed calculator.
This is from the guys at Far North Racing.
Check out this link.
I ran a BIG28 for about a year on my car. It was on the 2.0L for about 10 months, then after a month of down time I used it to break in my 2.3L. I absolutely loved that turbo. It's boost response was super fast and I never had a problem with it. If I was to do another dsm I'd make it a daily driven 2g w/ a big28 and all the supporting mods.
I am happy to finally see a thread dedicated to the T28.. I am interested in buying a FPBigT28 and what I really want to know, from all you BigT28 owners is: How is the top end (after 5500Rpm) with this turbo, compared to the stock t25?? I really like the stock turbo, but after 5500 rpm it doesn't pull that much... Is this the same with a Big T28 or not? And also is there a real difference compared to the T25 in power?
FP's Big28 comes ported already to "7cm", or 2.36" inlet dia, and yes porting is worth it. Buy the FP 17 psi adjustable wastegate actuator ($99), don't ask just do it Skip the 2.5" catback exhaust and run a 3" catback, again, you'll thank me later. Read this if you must know why: http://www.dsmtuners.com/forums/showthread.php?t=164893
I just looked at the Big28's compressor map (Garrett 62 trim 60mm) just to double check its performance envelope. Its compressor flows 35 lb/min @ 14.7 psi, and maxxes at 38 lb/min @ about 20.5 psi or so. Thats in 85* weather. It'll flow an extra 1% for every 10* temperature drop, according to Garrett's massairflow temperature correction formula. So going from 85*F to 30*F you'd actually be able to get 40 lb/min out of one, or 400 crank h.p.
It would fall in between them both.
interesting.. does the spoolup follow suit as well? and is it using the same 02 housing?
Yes and Yes.
its a na 4g63 with 9.7:1 compression..
the 6psi on it felt like a stock gst.. now im running 12 to14 psi ,it has no knock,runs on the richer side at wot (10.7 afrs) ..so i was thinking ..which turbo makes nice power delivry under 10-14psi (ei..which one is usable,as i want to keep the higher cmpression for throttle response around town)
thats my problem.. if you run to the redline..and shift, youll salready be out of the t25s usable powerband ,
please guys, contribute your experiences on the big t28
im fwd, i hope this turbpo will satisy for daily driving and sneaky autobahn roll ons.. im also trying to source a longer fifth gear (from a mitsu spacewagon) for more top speed on the bahn..
edit :im looking for a 300 to 350 fwhp