http://www.vetteweb.com/tech/vemp_06.../photo_14.html

I was looking at this link and it clearly states that the FAST 78 had better low end torque and hp up to 3500 vs the old 90mm FAST. When compairing it to the FAST 90 Graph:http://www.vetteweb.com/tech/vemp_0612_ls2_crate_motor/photo_15.html

Given that the 78 is no longer available new and the smallest new size is the 92, does the new 92 vary from the 90 to make more low end tq and hp?

Were the runner differnet on the 78 vs the 90 or just the snout opening size?

If it's just the opening size, could I just use a ported 78 mm or 80 mm TB and get the same effect of getting a little more low end torque?

Would appreciate anyone's time.


BTW: Heads and cam 346 ci

 

the runners were smaller too. Smaller runners means great air VELOCITY, and provides more low end torque.

this is why on the LS6 ( 346) the stock LS6 intake is just fine and the Fast 90 or 92 does not really do that much.

No the new Fast 92 does not make more low end torque. But for 402s, 418 ci they do wonders.

 

How about 427's (LS7's), what does the 92 do for them?

 

The FAST 78 and FAST 90 were identical except for the opening. The FAST 90 didn't give up any low end to the FAST 78 but they would produce the same results up to around 5,500 RPM where the FAST 78 would fall behind the FAST 90. The FAST 90 will give faster response to throttle movement. Tony Mamo has posted a lot of data on the differences.

My understanding is that the FAST 92 was modified in the opening only. I suspect the rest of the intake remains the same as it took them a long time to resolve some of the sealing issues early on and they likely would not mess with the final result having gotten it to work.

 

not much. The LS7 intake is very well designed


IIRC that was on the Fast 90s that HE ported, not the stock Fast 90s. on an LS6 block and LS6 heads. using his AFR205 heads was different.

 

I'm not sure how much clearer it could be that the 78 makes more power down low than the 2 dyno compairsons I attached in the links. I'm not dealing with ported manifolds or special conditions.

I havn't seen any posts by Mr. Mamo outlining the differences if any other than opening. If the opening made the difference, I could just put on my 80 mm tb to a new 92 and be done with it. It would be a lot easier to just get a new 92 rather than hunt and peck around for a 78 that is 75% as expensive as a new 78.

So paging Mr. Mamo, whats the deal with these bad boys? I need runner velocity to compliment my 205cc runner heads on 346 ci and it looks like the 90 and 92 suck wind to the 78 on low end torque #'s, flatness of the curve, and area under the curve.

Darn it would be easy if the stupid street warrior ever materialized.
This is obviously a joke, just like that manifold and the company.

 

Do a search on Tony and FAST. As for the article, this wasn't an LS1, it was an LS2 so not sure how much that affects the dyno runs that have been reported. As for the 78 and 90 (and I bet 92), the internals are the same.

Found a good thread. Link

 

the LS2 made a big difference over the LS6 or LS1.

But then again, many times we get to a point that each additional 1 -3 HP cost is exponential

 

I don't think you can easially can bolt up a 75-80 mm TB to the FAST 90 or 92 intake. The 90-92 mm TB are a four bolt design, the 75-80 are 3 bolt.

There are still a lot of FAST 78s around for good prices. Tony just ported a 78 for me.

The 78 and 90 runners are identical. If you have a ported 78 intake and want to go to a 90 TB all you have to do is replace the top portion of the intake which has the snout.

 

thanks vettenuts, I don't know how the 6.0 effects things down low with respect to the mani either, but up top with the 5.7 I imagie it would not run out of breath at all up top, which is sort of what tony was saying.

It answers everything except if using a 78mm tb on the 92 would bring the 92 unported performance in lign with the low end of the 78. I figure if everything else is the same, it has to be the opening. But that's all I can figure without having the tops of the manifolds.

It looks to me the 92 has a higher area on the snout where the top bolt of the tb would affix. Depending on if the 78's tb's back surface is totally smooth and wide enough would determine if a 78 could work on it.

I ran down to look at my stock 97's 73/75 mm tb and the edge of the machining was 91 mm, so your right that wouldn't work, but if the back of your tb is totally smooth like my 80 mm bbk and wide enough not to cause a gap to the seal of the snout of the 92 then it would work.

I don't know if the 78 mm z06 or 78 mm fast tb would work cause I don't have one to measure, but looking at the back of them, one could tell.

Certainly, getting one of many tb adapter plates on the market would solve everything if the smaller tb opening somehow generates the greater lower end power.

 

Wait a second:

Isn't the bottom pan larger on the 02 that's why you need to replace the valley cover bolts on the new 92? I don't know if the 78 makes you replace the valley pan bolts, but I havn't herd that before, which doesn't mean much.

Why would porting a 90, making the runner opening larger, increase it's low end torque when it would inversely affect the velocity of the air?

 

You rang?

What exactly are you trying to do??

Or should I say what are you trying to question?

To cut thru all the BS, if money wasnt an object and you were simply looking for the best results, you would purchase a properly ported 92mm FAST and compliment it with a properly ported LS2 90 mm TB....done....end of discussion.

From the crack of the throttle till redline at WOT it would be slightly stronger than a 78 mm version on the bottom and show you 5-7 more at peak with a ton more throttle response and SOTP from the swap (thats worth the price of admission in and of itself).

There is NO difference in the design of the intake and runners....only a larger entrance which is simply an airblade....and dont forget we are not relying on high airspeed to atomize fuel in the intake....the injectors are taking care of that for us further downstream.

It is NOT too big for a mild application 346, especially with a 205 AFR as the cylinder head itself speeds up the air and provides all the velocity that you need.....having more volume/flow in front of it simply creates a little less restiction which shows itself more upstairs when air demand is at its highest.

The heads determine the effectiveness of the intake swap....with a deep breathing efficient set of heads, the ported FAST 92 is still the heavyweight champ (for like four years in a row now) if you group the 90 and the 92 in the same playing field.

Find me a hard running combination that lays the smack on the chassis dyno (and the track) and the chance of that combo sporting a 90 (or 92) mm FAST intake is pretty high. Just glance around at the harder running combos...

The weaker the heads, the less the manifold becomes an effective swap because the weaker heads dont tax a stock intake like a much higher flowing premium aftermarket piece.

Hope this helps....

-Tony

 

the MAN has spoken


Thanks Tony

 

Yep he sure did and I really appreciate his time and clairification.

Tom was my HPDE instructor years ago and I always love to see his posts and replies. Always has SOLID advice, and I know what manifold he's running.

 

Dont believe everything you read or see under my hood.

The hamsters work hard down there

 

I believe EVERYTHING I read, especially the one about when you upgraded to lab rats.

For whatever reason my WTB post over in C5 parts started developing into a more technical post with good information and a great link to
ls1tech.


Here is the link to the C5 parts post:

http://forums.corvetteforum.com/c5-p...fast-78-a.html

Here is the ls1tech link

http://www.ls1tech.com/forums/dynamo...e-numbers.html