Forced induction works backwards of N/A. (blows instead of sucks) so building an engine for one and expecting it to do flips on the other is not what most people do. I seen a few people go to a 90/90 on a FI application and be pissed cause they gained like 9 hp.

 

While the fast might only get you a bit more hp than a ls6 or ls2 NA all evidence I have seen dyno wise shows that it does give a fair bit more hp and even more yet in ported form. While it might be worth 10 or so hp on NA it might indeed be worth more like 40 hp on a FI build.
I have seen many many builds with the fast 90/90 combo including aps own build and couple of 1000 hp builds in mags that are linked on the AFR website.

Can you make good power with an ls6 on FI ?Sure. You can also make good power FI with stock cam and stock heads. Will you make more power with fast intake, cam and better heads..YES..100% YES.% The more powerful and better flowing the engine is NA the more power its going to make on boost and off boost. or you can use less boost to make the same power as the weaker engine.

And you can get fast intakes pretty cheap these days used especially the 90s as guys trade up to the 92s.

And there is zero reason to run a burst panel under 20psi. The burst panels are set for think 38 or something which is really only for nitrous not many turbos are going to be boosting that range on f bodies.

Other reasons to run the fast are the direct port option which works great with FI, smalls shots supercool the intake charge and spool up the turbos instantly. Works fine with supers as well.

And you can also run the bigger tb less restriction than the stock tb.

I find it funny on these boards compared to most other fi boards. There its seems everyone knows you improve power by going to cams, better flowing heads and improved intakes..all the basic stuff of making more power. For some reason the fi guys here or many of them believe in doing it with stock stuff and just pushing the boost higher. This is the budget way of doing things and also don't take into account the off boost preformance which can be significant area on a street car. Same reason bigger displacement is good. More power on and off boost and faster spool up with more cubes . More compression can also be not a bad idea on a street car but many guys pick 8.5 some even lower for street cars. No need to do that with alc injection options, e 85.

But for budget builds sure run the stock intake, stock cam ,stock heads. But wouldn't say its superior way to go. Would just say its a way to go if you are stretching the budget.

And if I can make say 1000 hp at 15 is that mabye better for various reasons than to have to put out 20psi to do it.?Course simple psi numbers are also misleading and don't take into account air flow which is the true measure of power. A small turbo at 20psi does not put out same power as a big turbo at 20psi. Another common misconception I see on these boards. Thats why turbos have airflow ratings which you can see on the scanners. Push 52 pounds a minute and usually works out close to engine hp. 520 hp.
Push 65 and its 650 engine hp. Turbo will simply put out same power 650 engine hp potential at different psi on different engines. More effiicent engine also means it will put out some power at lower boost levels. And that is usually a good thing.

 

Hmm..well nice theory .

So you are saying your 5.3 in maybe stock form puts out same power as my built 408 off boost. That it could spin up the same size turbo equally fast?

Off boost is pretty important for a street car,especially heavy street car like my 4000 pound ta. Not as important obviously for race cars. I would guess my 408 NA makes around 550 engine hp. Your 5.3 off boost if its stock stuff ,talking stock cam,stock heads and intake is likely is making 300hp. There is no comparison at all there in terms of off boost power. Sure you spool up your snails and now you have some good power numbers at 4000 or maybe 5000 on a big snail on a 5.3 or 3000 if you go smaller turbo but then have less total power potential. Use smaller ar on the bigger turbo but then iit hurts top one of bigger ar to gain top but lose bottom and spool up.

Or you can have a bigger built engine like mine that spools them up like at 3000 rpm giving a much wider powerband and able to do it at less boost and still get the same airflow if we are talking the same turbo for direct comparison.

So again budget is budget .It works.And have seen some much higher than 9hp gains for a fast 90/90 on a big turbo build. Will have to post some of those dyno graphs or scan them..
And as said the nitrous option is handy as well. There is a good book on dyno
ls1 combos out .I have it. There are many FI and NA ,nitrous dyno charts and comments in the book. They aways keep repeating what I said.A stronger engine pre FI with cam,better heads and bettter intake is going to put out more power FI at same boost with same FI adder. its going to put out more off boost ,more hp ,more torque..all good things.

 

My 5.3 off boost makes maybe 175hp. Its bigger cam, intake and heads and small cubes dont work to well with 8.6:1 compression N/A. It would probably make decent power, but not till it hit an rpm that it wouldnt hold together....N/A. Stock it may have made 300hp... but now set up for boost theres no way. It has 6L heads on it, Vic jr, and a 224/ .580 112 cam.

 

Here is link to nice thread on a otherwise stock bottom engine. With good heads, decent upgraded cam and fast 90/90. Now too bad no before and after intake tests. And also peak hp doesn't always show the whole story and sometimes gains add up ,meaning its the combo of the heads,cam and bigger intake that make better power together than separtately.
Also the guy is making good power a nice powerband and is doing it at pretty low boost and low timing and safe afr. advantages of having a more power engine pre FI you don't have to push it as hard under FI and you get better off boost torque and hp and better spool up.

https://ls1tech.com/forums/dynamomet...ottom-end.html

Will try to post a few FI dynos with before and after fast 90 results.And bigger area under the curve is where it most of the time not peak numbers.

 

Ok so we are not arguing the benefits of better heads and cams just the advantage of a fast 90/90 over stock intake or ls6 intake for FI.

I just think that they are one more thing that can help the total numbers.
Just like underdrive pulley,cutout, can help too. A bit more here and bit more there and you get more in the end.

I could run zero boost in my current 408 and still have a nice powerful engine. It loses a bit from 9.5 but not that bad. And at a measly 7.5 or so psi with current twins likely would have 750 engine hp. And with very safe afr and timing.But never said it was a cheap combo.

 

I think rather than dumping $1300. on a 90/90 for like 10hp or less over the LS6, i'll do what everyone else does....turn the boost up like a half of a pound...and then maybe go by a candy bar with what I saved.

 

Well whatever floats your boat.. Your car runs some great times and is pretty light compared to some of our heavy f gens. Mine is likely 4200 raceweight. See how it does next season when build is finished.

I think one thing we can agree on is turbos work and work well.

 

me too!!!!

 

My buddy Craig has made well over 1000 HP with an Ls6 and run 7.20's in his car.

But, people think backwards when it comes to boost. Boost is a measurement of restriction. So, reduce that restriction and it takes less boost to make the same power.

Let me elaborate. There was a local guy with a GN with really good ported Iron heads on the car. It was a fast car. He swapped over to Stage II heads which flow about 100+ cfm more per port than ported iron heads. The net result was he made the same power at 10 psi of boost on those heads as he did at 28psi on iron heads.

On a FAST you do have the potential to blow out the seals. So, that is a potential issue. But, the long and the short of it is that improving intake efficency stand to return greater benefits in a FI setup than an NA setup all things being equal (which they seldom are)

Now, you can always turn up the boost to crutch any part of an inefficent design. But, the bottom line is that is that I would want the most effective setup I could come up with to make the best power on the least ammount of boost. But, if money is the overiding factor, there are plenty of people who have made good power with stock intakes and TB's.

 

Exactly J ROD.

And the fast seem to be no problem to 20psi. Above it might be worth looking the sheet metal or ls6 or new street warrior.

 

So whats everyone's insight, Victor EFI or a LS6 manifold??

 

For your setup I would stay LS6. We've used 90's many times and they work but you need to seal them very good.
I always prefer the carb intake over either of them though.

 

You just proved the other guys point with this statement, congrats.

The off-boost power is hurt even more by putting a FAST on it. anytime you aren't boosting it, you will be in an RPM that the LS6 intake works better than the FAST anyways. Same goes for these hogged out heads with stupid high flow numbers and big runners, sure they flow more, but at the sacrifice of lower RPM (aka no/low-boost) driveability.

Obviously the more an engine flows, the more power it'll make, but for a "street car" its a waste cause you'll never be able to hook that power up anyways.

 

On an NA motor I have not seen a FAST perform below an LS6 at any point in the RPM range even down low. I have consistently seen the FAST intake I have do better than an LS6 across the board.

 

I've never seen a dyno sheet read off-idle to 2000rpm, like when you are idiling around a parking lot with the clutch let out. Also, in my car the extra power wasnt noticable until after 4000rpm at WOT. but whatever, the fact is you arent going to notice a fast over an LS6 on a 5.7 or 6.0 when its out of boost.

 

I don't disagree that you probably will not notice it out of boost as well. My only point was that on engine and chassis dyno's we've seen across the board gains with the FAST, especially a ported one (like on from Tony Mamo) to correct the factory issues.

But, in a boosted motor its a toss up of better flow vs the potential for leaks. Many poeple will just turn up the boost over having a better flowing intake at lower boost levels. As I said above boost is a measurement of restriction. Too many people want to discount the importance of good flowwing heads and intakes and crutch them with turning up the boost.

That fine if folks want to go that way, but it should be noted that the increase in performance on a boosted motor of good heads and intake is actually greater than the incremetal gains of an NA motor.

 

I agree... and with less restriction/boost, there will be lower IATs also, which is another side benefit that'll net more power.

 

how do you know the ls6 intake is the restriction? on a d1 set up?

what about the shitty elbow? the maf in the way? the intercooler even.

alls i'm saying on lower (no offense) power combos the money is better spent elsewhere.

i am itching to finally get that new plastic intake that is taking forever.. and do a back to back comparison at different boost levels.

 

I had the fast 90 /90 combo before my 408 and turbo kits and see no reason not to try it out for awhile. I am not overly worried about it leaking and likely not going to be running much past 15psi ever absolute 20psi max. I also liked the fast is perfect for direct port which am adding. I think most problems with the fast leaking can be solved with a bit of rtv at key places between the shells and going to plug that hokey map hole and run my three bar off different place. Also will use blue loctite on the fast bolts that hold it to heads and the ones that hold the shells together. I also think some guys break the fast intakes as they supply special rounded bolts for the valley cover as the normal bolts will crack the fast intake and many guys buy them used and don't know this little fact.
Fast should make a one piece intake now in 92 size no real reason to make it able to be different sizes and it would be better for higher boost as a one piece like the ls6.

Anyway if it don't work out well then can always change it out but as said the direct port option is a required option.

As for my low end on my car its crazy enough with a 408 and current 3.42 gears.
I am not overly worried about the heads losing a touch of bottom if that is indeed the case as its a 408 not a 346. Ditto if the fast losing a bit of bottom also no big deal I have more than enough power down low more than can hook up. And the car pulls very strong thru the range its 7000 redline.
If did want a bit more low end for street could go with more gear, but car is going auto with 3400 yank stall anyway and 3.54 gears in dana s60. And could have went with afr 205s and maybe street warrior intake or something else.

But so far very happy with my combo. YMMV. I did leave my compression at a decent 9.5 and my cam is very streetable.