APS twin turbo on a stock 346 ls1

**Wesman** · 12-05-2008, 04:30 PM

Originally Posted by 99TAWS6

Guys have made big power thru yipe setups on twin turbos. A cutout helps immensely of course even single one in the intermediate pipe. True duals are great too of course but hardly absolutely necessary.

The fact that F-bodyBlur made amost 50WHP by opening the cutouts in front of a Y-pipe system says a lot about how well they flow. Everyone knows y-pipes aren't ideal in general, but on a twin turbo the restriction and poor flow really compromise the numbers.

**RedVertTA** · 12-05-2008, 05:24 PM

Originally Posted by Wesman

Thats a huge gain, no doubt due to the restriction of a Y-pipe system.

Thats the last thing I'd want to run on a twin turbo car, you have so much air to move and nowhere for it to go when both downpipes crash into a Y-merge.

I'd say at the mininum you would want 3" down to 2.5" duals, ideally 3" front to back though.

Why not just get a bigger y pipe? True dual is obviously best I'm not arguing that but its not always possible with some clearance issues.

I don't see why people are even surprised to see gains with cutouts. Under the normal y pipe setup you are merging two 3 in. pipes into another 3 when it meets the y, power loss seems obvious there to me with that setup, at least on forced induction.

**Wesman** · 12-05-2008, 05:33 PM

Originally Posted by RedVertTA

Why not just get a bigger y pipe? True dual is obviously best I'm not arguing that but its not always possible with some clearance issues.

I don't see why people are even surprised to see gains with cutouts. Under the normal y pipe setup you are merging two 3 in. pipes into another 3 when it meets the y, power loss seems obvious there to me with that setup, at least on forced induction.

You can only go so big before you run into clearance issues.

Size isn't the only determining factor either, it has to do with the way exhaust gasses flow through the pipes. A Y-pipe is one of the least efficient setups you can have, because you have a merge that involves pulses of exhaust gasses from each bank crashing into each other at one point and being forced together down a smaller diameter pipe. Basically its the worst setup for power and efficiency, regardless of size.

The most efficient setup is true duals, which usually incorporate and X or H pipe.

**zero_proto** · 12-05-2008, 05:39 PM

do true duals, but have them exit in front of the rear wheels. I was going to do that with my 99 but not anymore since i am selling the kit, but i am going to do that with my 69 camaro when the time comes.

**RedVertTA** · 12-05-2008, 05:52 PM

Originally Posted by zero_proto

do true duals, but have them exit in front of the rear wheels. I was going to do that with my 99 but not anymore since i am selling the kit, but i am going to do that with my 69 camaro when the time comes.

You could do that but cause of clearance they may hang low on 4th gens. I have a buddy that did that and his exhaust hangs so low you can see it without bending over to look underneath the car.

**zero_proto** · 12-05-2008, 05:53 PM

i've seen it done, and it looked perfect. That is why i was going to do, plus you don't have to deal with going over the axle

**RedVertTA** · 12-05-2008, 06:03 PM

Originally Posted by zero_proto

i've seen it done, and it looked perfect. That is why i was going to do, plus you don't have to deal with going over the axle

I didn't say it couldn't be done, just that there's more potential to screw up. I'm sure that if you just take your time on it and don't cut corners it should work out. Good luck on your build.

**qwkgto** · 12-06-2008, 03:41 AM

my question,how many of these guys have actual experience with a turbo setup? maybe a few .lets just say for the sake of argument for example mine is a ls2 10.9 to 1 stock compression I have for a fact ran 13-15 psi through this same ls2 stock cam,yes I have a set of 205 AFR heads but other then that all bone stock..so my point the stock ls1 has less compression then the ls2 why would it not like at least as much boost..... oh yea my mods are in sig..my custom kit with stock bottom end and cam seems to be kickin most of all the big kits azzes...facts a fact...keep it fat it will live longer..

**99TAWS6** · 12-06-2008, 08:35 AM

Not sure if the ls2 have forged or same hypercrap pistons the ls1s have. If they have the same and you are running that amount of boost that you said above then you are one lucky son of a gun.

I have many souvenirs of buddies running far less than that in my garage.I can take pics. Every one of them lost a ringland stock pistons are junk for FI.
Some of these guys were also pretty good at tuning not rookies or 16 year old kids.

Personally I would run no more than 7 to 8psi on stock engine with stock heads. Maybe 10 if had the 6.0 heads or equivalent to lower compression and I will still be prepared to do an engine if need be.
But the good news is forged pistons and good rod bolts are the too major areas of weakness on the stock engines. The cranks have gone to like 1000 engine hp. Rods are pretty strong factory also. Haven't seen too many bent rods.

Main reasons to go to forged crank is when you are stroking it .And of course you forge is you want more safety margins and to run higher boost levels.

**qwkgto** · 12-06-2008, 10:30 AM

Originally Posted by 99TAWS6

Not sure if the ls2 have forged or same hypercrap pistons the ls1s have. If they have the same and you are running that amount of boost that you said above then you are one lucky son of a gun.

I have many souvenirs of buddies running far less than that in my garage.I can take pics. Every one of them lost a ringland stock pistons are junk for FI.
Some of these guys were also pretty good at tuning not rookies or 16 year old kids.

Personally I would run no more than 7 to 8psi on stock engine with stock heads. Maybe 10 if had the 6.0 heads or equivalent to lower compression and I will still be prepared to do an engine if need be.
But the good news is forged pistons and good rod bolts are the too major areas of weakness on the stock engines. The cranks have gone to like 1000 engine hp. Rods are pretty strong factory also. Haven't seen too many bent rods.

Main reasons to go to forged crank is when you are stroking it .And of course you forge is you want more safety margins and to run higher boost levels.

Oh I agree .the ls2 has hypertectics just like the ls1 and the rod bolts are by far the weakest link they dont like it past 6800 so they say,I agree on the ring lands,I do have a new motor been on the stand waiting me to decide when im done playing with stock one,ive seen 18 psi on SBE of course its tuned for that when it sees that boost.plans for 20-25psi on stroker this spring.. so far my main issues with keeping car running has nothing to do with motor its transmission,heavy car + boost =broken trans...

**qwkgto** · 12-06-2008, 10:34 AM

here is one of my passes,drag radials just are not enough..http://s93.photobucket.com/albums/l7...01143253-1.flv

**RedVertTA** · 12-06-2008, 11:34 AM

Originally Posted by qwkgto

here is one of my passes,drag radials just are not enough..http://s93.photobucket.com/albums/l7...01143253-1.flv

I think I talked to you on another thread, are you the guy who had problems with the Fast manifold? Or am I an idiot getting you mixed up with another turbo goat guy?

**99TAWS6** · 12-06-2008, 12:31 PM

Go to afr website and look around.There are links to two 1000 hp big FI builds that use the fast intake.

One was originally using sheet metal intake but said the fast made more power or had a better power band or something like that.

They are fine to at least 20psi. Some guys crack the fast by not installing the supplied bolts in the valley .If you use stock ones the fast will crack when you tighten it down. This is common occurence when guys buy used fast intakes and don't know about the lowered head bolts being necessary. Also its inch pound spec tightening down the fast main bolts to block. Crank on those and you can also crack the intake possibly.

APS is also using a fast 90 on their forged up 346 build up dyno test engine.

I will have more personal experience data next spring with the fast up to around 20psi ,no desire to go past 20 and sure no need to.
Its having zero problems going 8psi so far. I do not like how fast has the map in the back though no hold down clip like factory so the map could come out under boost. I plan on tapping that hole and likely plugging it on my build just run my 3 bar with normal vacuum line.

**qwkgto** · 12-06-2008, 12:57 PM

Originally Posted by RedVertTA

I think I talked to you on another thread, are you the guy who had problems with the Fast manifold? Or am I an idiot getting you mixed up with another turbo goat guy?

yes that was me ,it was installed right,these ls motors are so freakin easy to work on,the fast are known to blow a gasket,ever seen them they are not much to look at as far as the gaskets, I have seen many of NOs guys blow em up..maybe I got a bad one from them,who knows,ill stick to the factory ls2 14 more hp for the money they charge you is crazy.to each his own.

**qwkgto** · 12-06-2008, 01:00 PM

Originally Posted by 99TAWS6

Go to afr website and look around.There are links to two 1000 hp big FI builds that use the fast intake.

One was originally using sheet metal intake but said the fast made more power or had a better power band or something like that.

They are fine to at least 20psi. Some guys crack the fast by not installing the supplied bolts in the valley .If you use stock ones the fast will crack when you tighten it down. This is common occurence when guys buy used fast intakes and don't know about the lowered head bolts being necessary. Also its inch pound spec tightening down the fast main bolts to block. Crank on those and you can also crack the intake possibly.

APS is also using a fast 90 on their forged up 346 build up dyno test engine.

I will have more personal experience data next spring with the fast up to around 20psi ,no desire to go past 20 and sure no need to.
Its having zero problems going 8psi so far. I do not like how fast has the map in the back though no hold down clip like factory so the map could come out under boost. I plan on tapping that hole and likely plugging it on my build just run my 3 bar with normal vacuum line.

I drilled/tapped mine and added a fiting so i could use a vacume line for the map,worked at least until the internal gasket let loose.

**99TAWS6** · 12-06-2008, 01:11 PM

Heres a guy running one on a d1sc at 15psi no problems.
"Depends on what level of boost you plan on running. The D1SC is capable of levels of boost that are most likely to high for the polymer 90 mm intakes, but some people run them at lower levels of boost with no problems. If you're heading to those higher levels of boost, you will want to have adequate engine components as well. I have a D1SC at low compression 8.78:1 on a 402. It's tuned to 13.5 psi and has seen as high as 15 psi in the cold, my FAST intake is adequate for this."

I think some rtv applied sparingly between the shells might help and also putting some loctite on the hardware holding the shells together. I would like fast though to make a one piece at some point or might switch to another make but I want it to have direct port option like the fast has.

I can find lots of other turbo guys that are running it to around 20psi or so.

**RedVertTA** · 12-06-2008, 02:37 PM

Originally Posted by 99TAWS6

Go to afr website and look around.There are links to two 1000 hp big FI builds that use the fast intake.

One was originally using sheet metal intake but said the fast made more power or had a better power band or something like that.

They are fine to at least 20psi. Some guys crack the fast by not installing the supplied bolts in the valley .If you use stock ones the fast will crack when you tighten it down. This is common occurence when guys buy used fast intakes and don't know about the lowered head bolts being necessary. Also its inch pound spec tightening down the fast main bolts to block. Crank on those and you can also crack the intake possibly.

APS is also using a fast 90 on their forged up 346 build up dyno test engine.

I will have more personal experience data next spring with the fast up to around 20psi ,no desire to go past 20 and sure no need to.
Its having zero problems going 8psi so far. I do not like how fast has the map in the back though no hold down clip like factory so the map could come out under boost. I plan on tapping that hole and likely plugging it on my build just run my 3 bar with normal vacuum line.

Look, I'm not saying you're wrong, just pointing out that there are people on this thread who differ. I don't have a turbo on my ls1 and Fast so I don't really have the right to argue any side of this.

You said the fast will hold up, and qwkgto said on an earlier thread that it wouldn't. Understand for the rest of us its confusing as hell when two people who have practically the same setup say the opposite thing.

**zero_proto** · 12-06-2008, 02:43 PM

it is not a perfect world, results are always different, even with the same setup.

**RedVertTA** · 12-06-2008, 02:48 PM

True to that, but its usually the rest of us that get a speech of what's the right route on a build instead of them duking it out with each other.

**99TAWS6** · 12-06-2008, 02:49 PM

Well I have searched and searched on both ls1.com and ls1tech and on google do your own searching but it seems its always second hand. Someone knows someone that has the fast have a problem.
I understand when you here two different views it is hard to know what to do. I gave one real reason for the fast to crack. Simply install it without the proper valley bolts that many guys don't know about if they get the fast used. That will crack it. Or tighten the intake manifold bolts to say ft pounds by accident instead of inch pounds. That also likely will crack it.

Rtv between the shells and some loctite on the hardware should work fine to keep it together.

LS6 of course is fine too and cheap. And one piece so for sure no problems and guys have run them to big power levels and high boost.
For my build I wanted the direct port option the fast has and am not going to go past 20psi. I have seen many many go to 15psi and some to 20psi with no reports of any problems at all.
You can also post about this on the ls1tech.com its pretty much the big ls1 board now that ls1.com this board sort of went downhill and lst1ech took over.
Both can have good info.

I welcome seeing any actual evidence of fast intakes cracking or breaking from boost alone especically under 20psi.
Most ls1 FI applications will be under 20psi. Factory short block ls1 FI should usually be under 10psi.

Those magazine articles mentioned on the afr website are running like 20psi on the dynos with big turbos.

and again there are lots of FI applications with the fast to 20ish psi in the ls1 dyno book. Not asking you to believe me without backing up what I say.

But if I had a dollar for some of the old wives tales I see on these boards I would be rich.

Not saying our friend with the gto is wrong either just want to see a bit more proof.
And that one mistake of not putting in the right bolts in the valley will crack the fast intake.