FAST 90/LS2 TB... TB causing problems?
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
FAST 90/LS2 TB... TB causing problems?
What's the skinny on using the LS2 TB with the FAST 90 on an LS1/6? Does it cause problems that only porting the throttle body will cure? If so, what porting is required in the TB?
Thanks!
Thanks!
Race Director
Joined: Sep 2005
Posts: 11,060
Likes: 291
From: Pasco WA
I continue to have some problems since I installed the FAST LS2 combo. I bought the manifold ported, but the TB stock. I initially had problems with stalling when I pushed in the clutch, but worse, annoying flat spots while at cruising speeds at low RPMs. Tony Mamo cured the flat spots completely by porting my TB, but it made the idleing a little worse. Now it mostly "hangs idle" when you push in the clutch. In other words, the idle stays at, or jumps up to about 1300-1600 when the engine is hot, and you're coming to a stop. It'll stay at that point for varying amounts of time; from 5 seconds, to sometimes 20, and even 30 seconds. It's not consistent. It's been to two tuners, BTW. Obviously, this' unfortunate, but the flat spots while at cruise were even worse. I just bought a MAP sensor relocation kit that may help somewhat, but I'm not holding my breath.
Former Vendor
Joined: Mar 2004
Posts: 1,518
Likes: 7
From: Valencia CA
I continue to have some problems since I installed the FAST LS2 combo. I bought the manifold ported, but the TB stock. I initially had problems with stalling when I pushed in the clutch, but worse, annoying flat spots while at cruising speeds at low RPMs. Tony Mamo cured the flat spots completely by porting my TB, but it made the idleing a little worse. Now it mostly "hangs idle" when you push in the clutch. In other words, the idle stays at, or jumps up to about 1300-1600 when the engine is hot, and you're coming to a stop. It'll stay at that point for varying amounts of time; from 5 seconds, to sometimes 20, and even 30 seconds. It's not consistent. It's been to two tuners, BTW. Obviously, this' unfortunate, but the flat spots while at cruise were even worse. I just bought a MAP sensor relocation kit that may help somewhat, but I'm not holding my breath.
I promise you with enough time spent it can be tuned out (the "cruise control" effect). If your at your wits end with it you can send it back to me and I will epoxy close some of the lower throttle position reducing the airflow there. You will notice a slight loss in the crispness of the throttle you enjoyed when you swapped on my ported unit, but everything is a compromise. Drivability issues with larger TB's can be a pain, and honestly thats when a talented tuner with alot of experience is really worth his salt. Also, some combinations (and vehicles) are just alot more finicky then others. Thats just the way it is. If you want me to make it a little less aggressive let me know....I would only need the TB for 3-4 days.
Drop me a PM if this is a direction you might want to persue...
Regards,
Tony
Last edited by Tony Mamo @ AFR; Jun 19, 2007 at 08:13 PM.
Race Director
Joined: Sep 2005
Posts: 11,060
Likes: 291
From: Pasco WA
Thanks, Tony. As I said, the flat spots were a much bigger problem, and your totally eliminated them. Other than idle, the car runs fantastic. Very crisp throttle response, and even good mileage. Anything off idle is butter smooth. I've still got a few things to try, but I don't think I'll have the epoxy done. I don't want to give up any throttle response. It honestly feels better than my old '67 SS350 with a Holley 650 dbl. pumper, and it only could get 9 mpg. 
Burning Brakes
Joined: Nov 2003
Posts: 790
Likes: 7
From: Denton TX
I have the very first FAST that Tony Ported for anyone other than himself. At one time I had a Nick Williams 90mm on it. At this point I have a 402 with an LS2 TB on it. I can only make a guess but my guess is that your tune needs to be adjusted. One of the things that was originally missed on mine is a parameter that defines the area of the TB. This was not tuned when my LS2 TB was originally installed. I had problems keeping the car running until it warmed up. The follow up tune corrected this and the car now runs great.
A highly modified 402 with a 90mm TB is a long way from the original 346 that the PCM was designed to control. My experience has been that you really need a tuner who knows the process well to make the PCM work with a larger displacement engine.
A highly modified 402 with a 90mm TB is a long way from the original 346 that the PCM was designed to control. My experience has been that you really need a tuner who knows the process well to make the PCM work with a larger displacement engine.
Former Vendor
Joined: Mar 2004
Posts: 1,518
Likes: 7
From: Valencia CA
I have the very first FAST that Tony Ported for anyone other than himself. At one time I had a Nick Williams 90mm on it. At this point I have a 402 with an LS2 TB on it. I can only make a guess but my guess is that your tune needs to be adjusted. One of the things that was originally missed on mine is a parameter that defines the area of the TB. This was not tuned when my LS2 TB was originally installed. I had problems keeping the car running until it warmed up. The follow up tune corrected this and the car now runs great.
A highly modified 402 with a 90mm TB is a long way from the original 346 that the PCM was designed to control. My experience has been that you really need a tuner who knows the process well to make the PCM work with a larger displacement engine.
A highly modified 402 with a 90mm TB is a long way from the original 346 that the PCM was designed to control. My experience has been that you really need a tuner who knows the process well to make the PCM work with a larger displacement engine.
It must be going on four years at this point. I also remember (at the time) when every other person's opinion on the Internet was why bother....now if your serious about making power and dont have a ported FAST people think your crazy....
Your exactly right about the tune....the new engines very different VE (volumetric efficiency) and the larger TB's airflow characteristics versus blade percentage opening have to be properly matched for seamless performance. The factory spends alot of time on all those tables to make sure that is the case (with the stock TB). Once all those parameters are changed its a different ballgame but the better tuners who take a more scientific approach (and less trial and error) can get the job done in most cases.
Andy...drop me a PM one of these days and let me know where your at with your future project(s).
Regards,
Tony
Racer
Joined: Oct 2004
Posts: 370
Likes: 1
From: Tracy CA
I've got the FAST 90/LS2 TB, both ported by Tony, and I don't have any issues. Car runs pretty darn smooth all things considered.
Having driven my car, wouldn't you agee Tony?
-Rick
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Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
Guess that is one factor that I don't worry about, the tuner I use is one of the best out there and fortunately for me is local. When I take the car in for a tune, he also spends more time on the road than the dyno to ensure that street driving is nailed down really well. Maybe that is why I don't have any issues 
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
Thanks for all the info guys!
My car will be staying a 346 inch motor for the foreseeable future.
Tony: Can the car be tuned to work properly with a FAST90/LS2 TB leaving the LS2 TB stock? Is the porting actually required for smooth running or is it just to increase throttle response on tip-in?
What is the difference between the NW and LS2 TBs? I know the LS2 TB has a large area at the bottom that seals off to the bottom of the throttle blade long after the top has begun to open and allow air through... I believe this is done to "numb" the throttle response a bit and make the car less sensitive to throttle tip in. Is this the area that's removed during porting? If so, is this necessary? Does the LS6 TB have a similar feature?
Thanks!
My car will be staying a 346 inch motor for the foreseeable future.
Tony: Can the car be tuned to work properly with a FAST90/LS2 TB leaving the LS2 TB stock? Is the porting actually required for smooth running or is it just to increase throttle response on tip-in?
What is the difference between the NW and LS2 TBs? I know the LS2 TB has a large area at the bottom that seals off to the bottom of the throttle blade long after the top has begun to open and allow air through... I believe this is done to "numb" the throttle response a bit and make the car less sensitive to throttle tip in. Is this the area that's removed during porting? If so, is this necessary? Does the LS6 TB have a similar feature?
Thanks!
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
As mentioned you need a good tuner. I had the same problem with my car initially. I had Allan Futral tune it and it took a little while to get it to my satisfaction. He managed to get ride of all the up and down the car was doing because of the big cam. He also stopped the hanging throttle as you are experiencing. It is very important to have a good tuner.
Former Vendor
Joined: Mar 2004
Posts: 1,518
Likes: 7
From: Valencia CA
Thanks for all the info guys!
My car will be staying a 346 inch motor for the foreseeable future.
Tony: Can the car be tuned to work properly with a FAST90/LS2 TB leaving the LS2 TB stock? Is the porting actually required for smooth running or is it just to increase throttle response on tip-in?
What is the difference between the NW and LS2 TBs? I know the LS2 TB has a large area at the bottom that seals off to the bottom of the throttle blade long after the top has begun to open and allow air through... I believe this is done to "numb" the throttle response a bit and make the car less sensitive to throttle tip in. Is this the area that's removed during porting? If so, is this necessary? Does the LS6 TB have a similar feature?
Thanks!
My car will be staying a 346 inch motor for the foreseeable future.
Tony: Can the car be tuned to work properly with a FAST90/LS2 TB leaving the LS2 TB stock? Is the porting actually required for smooth running or is it just to increase throttle response on tip-in?
What is the difference between the NW and LS2 TBs? I know the LS2 TB has a large area at the bottom that seals off to the bottom of the throttle blade long after the top has begun to open and allow air through... I believe this is done to "numb" the throttle response a bit and make the car less sensitive to throttle tip in. Is this the area that's removed during porting? If so, is this necessary? Does the LS6 TB have a similar feature?
Thanks!
At least 5 RWHP and a few of my customers have seen close to 10 RWHP (tuned versus tuned btw) but that is more the exception than the rule. You need the porting to get the most benefit from the FAST 90 swap....especially if the manifold is ported as well. Plus the improved drivability and response is key....once you experience it you couldn't go back to a "lazy" TB set-up. The engine would feel lethargic if you did.
Didnt see the thread come back up or I would have replied sooner...
Cheers,
Tony
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
Le Mans Master
Joined: Dec 2005
Posts: 8,475
Likes: 332
From: Port Arthur, Texas 77642
On my previous setup with LS6 intake, ported TB, ported de-screened LS1 MAF I had the same issue. I upgraded to the "Mamo Ported" FAST 90/90(LS2) setup but also added a C5 ZO6 MAF with integrated IAT sensor. All this on my FI setup really took some work from my tuner(John Page/21st CMC), but being an experienced tuner with a no compromise mentality he nailed it!! No idle issues at all, and like Tony Mamo said, the throttle response with the "Mamo Ported" LS2 TB is amazing. I did not need a dyno to tell me what I was feeling, SOTP was much more crisp. Just blipping the throttle makes the revs climb much faster 
