need more of a midrange!

[Big28 2gFWD]

1st things 1st here's my set up. 99gst full weight sbr big28, 550's, comp cams 101100's(264 equals) 3" turbo back (stock 2g o2 housing) greddy big fmic, plus wires, all the basics. tuning on an s-afc.(39% lo 79%hi tp.....1:-8, 2:-12, 3:-26, 4,5,55,6,7:-28)

ok now down to business. altho im only mildly upgraded, not many cars in my area give me alot of work from a roll. untill tonight line up with a turbo'd trans am(366whp) we start the pull at around 50 and he jumps instantly about 1 1/2 cars and holds it til i slowly start to creep up on him, he gets off it race over. im used to playing catch up, as my boys srt-4 always jumps me, then i usually blow his doors off after reeling him in. couldnt really do the same on this t/a tho, too hard to reel him in, i think if i could of stayed with him off the third beep i would of creeped past him.

i watch my s-afc, and karman readings peaking at about 2052(18ish psi) wonder if thiers anyway i get flowing that much early in the rpm range so i can use the power longer, i dont even break2000hz until 5800rpm. any suggestions? going to a 3"o2, taking off hi flo cat and running test pipe? something with my tuning? boost is set via profec b with curve all the way sharp? i just want a more powerful midrange to make up for the torque some of these domestics are putting down..

thanks

 

[bfdahl]

I would log it and see what your timming is like, there is big power in the midrange if your trimmed correctly. Im running a simmilar setup and once the knock was gone tha power was there!

Drop the boost to 15 psi and tune for max timming and then turn it up little by little to see where it starts to pull timming and back it down a notch or get bigger injectors.

 

[CanadianTSi]

Taking out the cat would help.

Honestly though if you can keep up with a 360whp car then it sounds like you have your T-28 pretty much maxed. I would suggest a bigger turbo

 

[evolvingGS-t]

Have you thought of adj. cam gears?

 

[pboglio]

1st things 1st here's my set up. 99gst full weight sbr big28, 550's, comp cams 101100's(264 equals) 3" turbo back (stock 2g o2 housing) greddy big fmic, plus wires, all the basics. tuning on an s-afc.(39% lo 79%hi tp.....1:-8, 2:-12, 3:-26, 4,5,55,6,7:-28)......

.....i watch my s-afc, and karman readings peaking at about 2052(18ish psi) wonder if thiers anyway i get flowing that much early in the rpm range so i can use the power longer, i dont even break2000hz until 5800rpm. any suggestions? going to a 3"o2, taking off hi flo cat and running test pipe? something with my tuning? boost is set via profec b with curve all the way sharp? i just want a more powerful midrange to make up for the torque some of these domestics are putting down..

thanks

Looking at your mods list and the fact that your running only 18 psi, you've got at least another 40-50 h.p. left in your setup. Before most of the mods I'm about to list, I was already running 35-36 lb/min on a T28 with 22psi & 100 octane race fuel. I'm well beyond that now on my 20-21 psi pump gas setup, which is how I drive my car everyday. You need to bump the boost pressure up a bit more though. The Garrett 62 trim (FPBig28) compressor map shows 37-38 lb/min at 60% efficiency and 85*F, more in cooler weather. If you are hitting those airflow numbers now than I would say its time for an upgrade. But the 18 psi setting tells me you're not even close to maxxing the turbo, 21-22 psi on a properly supported T28 is a pretty big difference from 18 psi, especially in the midrange.

Anyhow, according to my T28 logs, a testpipe picked up about 1 lb/min or 10 h.p over a highflow cat. I run a 4" cold air induction setup which dropped my precompressor intake temps by 20*F on average, which is another increase of over 1 lb/min (10 h.p.) in compressor massflow at the same boost pressure. Do you have one of those aftermarket hard compressor intake pipes? If not then get one (I have the RRE 2.25" $45 intake pipe) because they are worth about 1-1.5 psi more of boost pressure by reducing intake pressure drops. If you don't have the FP 17 psi wastegate actuator then get that first, that probably provided the biggest "hit" of torque of anymod I've done to date, bar none. Instead of the boost kind of waltzing up to 18-20 psi, its now more of an explosion of torque that makes the rear end squat down hard when the boost hits. This provides that essential 1/2-1 car length leap needed during a rolling race.

Dejon's CBV stop leak valve/kit helped my turbo hold steady boost to redline, before it would completely blow open and overspeed the compressor wheel in attempting to maintain the intake manifold boost pressure. A 1st gen 60mm throttle body provided some really nice midrange/topend gains even when I had my T25, really surprised me. Running DSMLINK and jacking up the ignition timing curve about 3-5* everywhere also provides quite a nice bump in midrange and topend. Turbine housing/Exhaust manifold port work (6cm style) was worth a consistent .5 lb/min or 5 h.p. Dumping the stock 2g maf and going VPC was worth another 10-15 h.p. (DSMLINK) due to holding higher boost at higher rpms. Maybe something like the MAFT would work for you, I just happened to have a spare VPC laying around. The midrange power hit is violent without the MAF restriction. How big is your airfilter. I've upgraded K&N airfilters 3 times, I'm now using a 7.5"Dx9.5"Lx4" cone rated for 1000 cfm and even that thing drops a measured .9 psi pressure drop. Gotta do all the little things to get the most out of your setup.

At this point you should be able to run 20-21 psi 93 octane pump gas without overspeeding the compressor or knocking, I'm able to anyway. Testpipe ($50), MAFT ($350)/VPC/etc, used 1st gen 60mm Tbody ($50), high spring wastegate actuator ($99), Dejon CBV stop leak valve kit ($50), huge K&N airfilter ($45), DYI cold air induction, etc. etc. and 20-21 psi pump gas should net you quite a bit more midrange without the need to upgrade to a larger turbo.

I think for the FPBig28, the main goal is to get the boost/torque to hit very very hard and fast, run as close to 20-21 psi on pump gas without knocking and overspeeding the turbo, and maintaining as much boost near redline as possible. Hope this stuff helps out. Cheers.