Earl H

iTrader: (1)

Alright, I've done all the searches but I want to just come out and ask the question to some that have tried:

Current setup:

Forged 346CI, Ported LS6 Heads, T76GTS Single Turbo...care makes 740rwhp/725rwtq.

After experiencing a TT Big Block car, I recently made the decision to change my setup to a 402CI Stroker, Twin Turbos (T3/T4 hybrids) and AFR 225s.
I've already purchased the twin turbo setup, sold my single turbo setup, purchased the AFR 225s and put my forged 346 up for sale.

My tuner has all but successfully talked me out of the 402CI, due to its inability to rev. (oh yeah, I need to be able to spin the motor to 6900 - C5, A4 and 3.42 rearend) in favor of keeping my stock cubed forged short block that should rev to 7K w/o incident.

Now that I have decided to keep the s/b and I have the AFR 225's (72CC). I'm wondering if I'll get the desired results...good mid and top-end flow, low 10 sec. time slip @ 145mph on et streets. I know that it is said that low-end will suffer, which I'm not really worried about with the twin turbos.

How many of you guys out there have similar setups? Can you list the power that you've made? Track times? Street-feel? Any issues? Thanks in advance for the feedback. Oh yeah, what head gaskets?

V8_DSM_V8again

I have AFR 225 & 205 data pluged in EAPro for a 6.0 I am building... It was dead on when I did it for my AWD 2.0 DSM...

A head with numbers like the 225 will definately help get you there.. Even a AFR 205 with the exhaust CNC work and exhaust valves of the 225 added will help...

It all depends on what the turbo system is...

I need to know every little detail about the system....

If I can get low tens in a full weight 2.0 AWD car you should with your TT..

A AWD DSM is not too far behind a f-body believe it or not.. Tcases and extra CV shafts are heavy.... They are just to "popular" since F&F so I am going back to the bowtie.....

RyanJ

A 402/408 will rev to 7000+ rpm...easily. Are we saying that the T3's turbine will not flow the exhaust a 402 will be putting out at 7000rpm?

mdhmi

iTrader: (1)

One of the F1 blower guys on CF switched from worked over 6L heads to AFR 225's and picked up about 5-8 hp. The reason he didn't pick up more is because the 72cc chambers of the 225's lowered his CR.

Why not try an LS2 with a stock crank? 366 cubes. You're not going to have any trouble running well into the 10's with either your current forged 346 or an LS2 based 366 with the TTi X kit.

Cheers,

Mark

V8_DSM_V8again

It depends on his pistons and gasket thickness... Also he may want a lower compression ratio turbos can run ALOT of boost efficiently...

Earl H

iTrader: (1)

How much did he lower compression? There is a formula for hp drop per 10th in compression drop. Also, if he didn't change out his pulley and still saw a gain of 5-8hp with the change in compression, then I'd say all things considered...he did pick up something...now quantifying it is another matter. Regarding going LS2 with stock crank..I thought about it, but in the end, if I'm going to go big bore, I'll wait till the current block goes and then go with the new Escalade or LS7 block w/ stock crank for more cubes/bigger bore. Doesn't make sense to spend $6K for the swap just to pick up an extra 15 cubes now when there might be more/better/cheaper options down the road.

V8_DSM_V8again

What pistons are in the block now... Dish in CC's and bore?

ddnspider

iTrader: (26)

If the AFR 225's have a 72cc combustion chamber it wont change the compression from 6.0 ltrs as they also have 72cc chambers.They'll flow better as well as having a thicker deck so youll be able to run more boost before lifting the heads given a good tune.If you have them, use them.
ull definitely drop the CR going from ls6 heads to AFR's but it wont be enought to matter.you'd drop less anywhere from .5-1 point but ull be able to run substantially more boost with that lower compression.

Earl H

iTrader: (1)

3.905 bore
-8.99CC dish

mdhmi

iTrader: (1)

I think he went from 66 or 67 CC 6L heads to 72 CC 225's. So whatever that translates to in CR.

Mark

ddnspider

iTrader: (26)

as long as these werent milled or chamber work was done they have the same combustion chamber so same compression ratio,AFR's just flowed better in that case than the 6ltrs thats all

Earl H

iTrader: (1)

Well my current heads are 66cc and my compression ratio is 9.4:1. Going to the 72cc AFRs would take me down to 8.8:1. Does anyone know the the formula for compression vs. hp?

ddnspider

iTrader: (26)

i believe PSJ said it was a whopping ~3% for every point in compression dropped just as a ballpark figure.youre dropping .6 of a point so youre looking at approximately 1-2% drop in hp...big whoop as u can run alot more boost with the compression that much lower.it was a good move.

V8_DSM_V8again

There is'nt a formula for that..

There are alot of other factors involved...

Like those turbo specs you gave me..

I know that turbine and compressor combination well...

You are going to be fine with those pistons and the bigger chambers but get a thicker head gasket... A SCE ICS Titan...

Anyway shoot for 8:1 CR...

Keep it low that is a turbo that reall likes boosting heavy and is really only at its potential efficiency when doing so...



Pressure Ratio = (boost + 14.7) / 14.7

25psi = 2.7

Its still 72% efficient there.. A big fat *** area of 72% efficient...

At 22psi you are still 79% efficient depending on how much air you are moving at that pressure ratio...

2001-WS6

Earl you know the answer is going to be a big fun yes.

The 402 with AFR225s (out of the box with some good dual springs) will spin these kits like a top. So the boost is just a toe-in away when you want it and just a twist of a **** to hit the low 10s at 145mph.

Rick

NicD

iTrader: (7)

Well my setup is similiar. 347ci, 8.4:1 compression, T-76GTS, AFR 225s w/.040 cometics, and a custom FTI turbo cam.

It made decent power so far but I have been holding back while I put this second pump in the tank. 665 rwhp on 10 psi with 91 oct and it could probably go a bit further with 91 oct but I just haven't bothered to push it. I figure if I want more than that I will run the good gas and turn that **** up. Feels great on the street, nice and smooth and quiet until I get into the loud pedal. Haven't brought it to the track until I can get stable fuel pressure with the second pump in there.

Pro Stock John

iTrader: (34)

Was your old combo kind of peaky, I went 145mph with 680-700 rwhp a few times this year with the blower setup.

With say 800rwhp, on slicks, I'd be shooting for 150mph.

Seems like TT's vs single, that you can get to a number with either, just the twins will spool up better... But that's not an issue if you are sitting at the line taking your sweet time to build boost during a TnT nite at the track.