verbs

Being that I eventually plan upgrading to a stroker/bore motor down the road, I'd really only like to purchase one FAST LSX intake manifold now, being the 90mm piece.

Is there any reason for me not to run a 90mm piece with my heads/cam 346ci car right now? Could it very well hurt performance? If it doesn't hurt my 346ci performance now, I'll go 90mm. If it likely will hurt my current performance, I'll go 78mm.

Camaroholic

iTrader: (1)

IMO, the less restrictive, the better.

My H/C LT1 car fragged the motor earlier this year, and in a pinch, I bought a cheap 4.3L L99 from a Caprice, and threw it in my '94Z. I'm running a 58mm BBK Throttle Body (stock is 48mm). Any negative effects? Hell no. Throttle tip in is fine. WOT is fine. No problems at all. Is it a waste? Are there gains? Maybe. But I already had the BBK. So why not.

90mm will not hurt your performance. Just your wallet. Will it be worth it? That choice is up to you. When the FAST comes out, there's no doubt a 90mm will be going on my 346ci car.

-Andrew

jmX

Considering the product isnt even out yet, it sure makes answering questions like this a bit difficult. For all we know it'll flow less than an LS6 manifold.

Also, moving this to external engine.

quickWS6

What is everyone gonna do about a 90MM TB? Has F.A.S.T. announced one yet and a price?

Beast96Z

iTrader: (21)

I bought the 90mm version, but plan on using the stock ported TB until I go bigger cubes. I don't see the actual intake itself being diffrent, just the TB opening.(I hope)In that case, as long as the stocker still has the same bolt pattern as the 90mm, you should be able to run the stocker, then upgrade with the cubes later. But then again, why would they offer the 2 versions if a stocker worked on both. I wish I could get the company I ordered from to answer the questions for me, but I don't think they know either.

verbs

The 90mm intake will bolt up to the stock throttle bodies according to FAST. So you'll have to use a smaller TB until the 90mm is on the market.

quickWS6

Sounds good!

verbs

My biggest fear is that the 90mm intake opening will kill the velocity of the air coming in from the 78mm TB, which may cause me to lose power. Also, going from a 78mm TB to a 90mm Intake may cause turbulence as well.

Does anyone else share these same sentiments?

Beast96Z

iTrader: (21)

I don't see where there would be any diffrence? The air coming in does not know that it is falling into a 78mm hole or a 90. If the intake tract of the intake was longer, then I would worry, but it looks to be only about a inch wide. This is just my opinion, I would love to hear other thoughts as to whether or not they believe it would cause intake turbulence.

pewter99SS

I'm very interested in this as well. I currently have a TSP 85mm lid and 85mm Maf and I would prolly upgrade to the 90mm TB and intake if it does prove worth it. I think there would be a little tubulance in this case going from 85-78-90, but I could be wrong. The direct port nitrous plums may be enough to sell me on the deal though.

verbs

Bernoulli's (sp)? Principal tells me that will reduce air velocity a ton coming into the manifold.

My plan was to use an 85MM TSP lid, 87mm Silverado MAF, and 90mm LSX intake.

pewter99SS

that is what I thought.

That Silverado Maf is a good idea, but what about the TB?

verbs

FAST sells a 90mm TB to go with the intake, problem is it won't be ready until February.

In the mean time, I was going to dremel the back side of my TB so it opens up in the back at a 45 degree angle to reduce turbulence a bit.

I did confirm that the 78mm TB will bolt up to the 90mm intake.

ms4

Any time you change the diameter of the intake anywhere along the way, you change the characteristics of the air flow. In this case, going from 78mm to 90mm will cause the air velocity to decrease. Generally speaking a mismatch is definitely NOT a good thing. Specially if its a sharp non radiused edge, which I presume would be the case, since the idea eventually would be to have matching 90mm bores from the TB to the intake. The edge would definitely cause turbulence. So not only are you decreasing velocity, but you are introducing turbulence. Probably not such a good idea.

In reality, it may not make much of a difference anyways, since the the plenum's cross section is no doubt greater than 90mm anyways. The air velocity will decrease as it enters the plenum and then increase again as it gets squished down the runners. Some time on a flow bench should easily show the impact of the 78/90mm mismatch. But to do that, we would need an LSX intake, and uhm, well... heh. they're not on the market yet.


just my 2 cents anyways.

John02SS

iTrader: (47)

I think it might hurt some in the high RPM's. I had a Mustang before my SS and when I put a 70mm TB on it over the stock 65 the car would lay down past 5500 when the smaller would make power to 6000. I dynoed with and without and the larger TB would gain 1-2 HP in the curver, but lose 15 past 5500. A couple of us had the exact same results. I guess the gain in volume wasn't worth the loss in velocity. Same principle as porting heads out to the point they lose velocity that is needed. But again this was on a 4.6 Mustang so a H/C stock cubed LS1 may not react the same.

bodhi

What is the pricing for these? the 78mm? the 90mm? When are they actually going to hit the stores?

pewter99SS

Tbyrne is taking pre-orders for them
78mm = $789.99
90mm = $869.99

www.tbyrne.com