This intake has been nothing but a pain in the *** since I bought it. I've done a bunch of searching and it seems like a common problem. I had the truck at my tuner and he was telling me I had a vacuum leak at one of my injectors and that was probably causing it. I fixed that and it still doesn't want to idle. I'm also using the fast 102 throttle body. This is on a lq4 with torquer v2 cam and 243 heads. If i switch over to a ls6 intake am I gonna see a huge drop in power? It made 410 rwhp and 398 ft lbs on my current set up. Just frusturated at this point. Any other intakes you guys recommend?

 

Yeah a new tuner

 

Likey not the intake that's causing poor idle quality. You could have your intake smoke checked through the TB opening after all escape paths are blocked off or crimped closed by a local shop and if done right it will find any and all small leaks, this is the method most people use to find unmetered air leaks . If I Remeber Fast uses a slightly different injector o-ring size, you might look into that and if you find no leaks start looking at IAC and tune. be sure your TB stop is set correctly, do an IAC relearn if it is.

 

This thread has the best comments and suggestions I've found on getting the LSXRT driveable. There are screen shots showing idle changes for the tune.

https://ls1tech.com/forums/pcm-diagn...g-issue-2.html

I had an LSXRT & 102 TB Nick Williams on my 91 RS 383 LS1 with a 229/229 cam. The LSXRT sucked it was horrible to drive and still sucked after over half a dozen tuning sessions with two expert tuners.

We dyno tested the 102 Fast LSXRT , LSX92 and a customer Peak ported LS6 with the 90MM TPIS snout. Same day, same water and air temperature. The Peak ported LS6 with TPiS snout ball stomped both fast intakes. In area under the curve for horsepower and torque, in peak hp and in peak torque. Driveability was stock with the mod'd LS6 intake. In fact two other people that drove my RS said they'd give up 30 hp to get rid of the LSXRT and it's horrible driveability. Amazingly the RS gained hp and torque and driveability.

The PP LS6 TPIS made 2 hp peak more than the LSXRT in my dyno testing on my small cam stroker.

I don't think my findings would be true with big cam high rpm set ups but with a smaller cam and 383 or less cubes, I wouldn't be surprised if a mod'd LS6 intake was superior in performance and driveability in many cases.

For your car the Fast LSX 92 might work well.

It might be worth trying the LSXRT with a 92mm TB...I didn't do that.

Also the 102 stuff is harder to tune with a 24x crank and the older slower PCM that uses cable TB.

Best wishes

 

Ls6 intake out perform a Fast LSXRT? I'll disagree with you on that one, if it's tuned correctly. Fast made that intake as a performance upgrade for trucks and SUV's, I doubt they made it difficult to tune or released it knowing it would have drivability issues.

 

It is not a matter of my opinion or what you think - it was tested on the dyno, the result was consistent and repeatable. It is a stone cold fact the PP LS6 TPIS intake dominated. All of the intakes were tweaked and tuned for best results.
​​​​
We were all shocked. Actually flabbergasted is a better description.

The Peak Ported LS6 intake with the TPiS 90mm snout out preformed both Fast intakes in every measurable category on my small cam 383LS1. The harmonics and combination of parts in my 383 LS1 engine simply made more power everywhere with the tricked out LS6 intake.

I've discussed at this result with several experts, one of which did cylinder head development for Katech - and all of them said it's quite possible, engines aren't steady state like a flow bench, harmonics and other factors come into play. They all also suggested that with more cam and more rpm my trick LS6 wouldn't keep up with the Fast intakes.

With a big 236/242 cam I think the Fast intakes would have excelled.

Speaking of Fast, they were no help when I tried to contact them severally times. I gave up.

With drive by wire TB, 58x crank and the newer more powerful PCM's the LSXRT might work OK. With the older cable TB's, 24x crank and slower 2002 LS1 PCM the LSXRT is far more difficult to get dialed in with great driveability. I also suspect more cubes is 400+ make it easier to dial in.

There may be some who get the LSXRT to work with the old PCM's. After I switched to the PP LS6 TPIS intake, I met one of the honchos (owner?) at HP Tuners at the PRI show last year's. He introduced me to a tuner that has been able to take most of the Fast 102 LSXRT issues. I will see if I can find the contact info.

Getting power is pretty easy compared to dialing in driveability - unless my RS gets a bigger cam there's no reason to try the LSXRT on my car again - it under performed with my current set up.
​​

 

AOD92,

Have you confirmed the TB blade is perfectly centered in the TB with a feeler gauge?
When chasing after my LSXRT's issues, the engineer at Vararam said that is one of the most often over looked issues in tuning 102 TB set ups. Off center TB blade can effect airflow and the Idle control counts.
He also said make sure the TB seals correctly and check for vacuum leaks.

As a band aid - a slow idle decay so the rpm drops gradually can help with idle issues.

Unhooking the IAC and manually crack the TB open so the car idles with out IAC, can help some then tune for driveability . This way the car should not die due to slow IAC response. Then plug the IAC in and let it help.

 

I do have the older pcm, 24x crank, and a dbc tb. It's really aggravating. I d heard a few people saying they're drilling their tb blades on the 102 because the iac opening isn't big enough. That might be my next step

 

That's very true of the fast 102 TB. I've read several places that using the Holley 105 TB is much easier to tune but I have no direct experience with it

 

I'll do someone a favour and trade them an ls6 intake for their 102 straight across

 

Tuning a DBC 102 TB is the worst thing on a Gen III PCM. They just struggle with it.

With that said, I've tuned quite a few of them after I went through a few cam combos and TB combos on my car. It's not that hard to do it. But you have to basically throw away all the idle air routines for the stock car. It's the one place where you can't really use the stock tables as a baseline. You have to start over.

IAC effective area table will end up looking very different depending on how far you end up having to crack the blade or if you have to drill (I had to drill mine). And with the FAST, you may have to ream out the IAC passage.

So it's not really a bolt on and go solution. Not at all.

If you have HPT I can help. Otherwise, you'll need to take to a place that has specifically tuned that TB.

And to say the LS6 can outgun a FAST... well, consider the LSXRT is the best FAST has ever put out. It has a huge plenum and straight, short runners. You have to cam it differently than you do an LS6. But it will walk it.

It puts a hurting on the MSD AirForce for Cathedral ports. That giant plenum is why.

 

Pretty much spot on. Your idle prop, int, and derive tables are almost a complete do over. Especially SD.

But in my case, the MSD walked the LSXR. It could have something to do with the cam. I still think there comes a point when the cam IVC gets late enough that the shorter runners are better match for the cam and vice versa.

 

It's not a matter of saying it Jake. It is a matter of FACT. We dyno tested LSXRT vs LSX 92 vs Peak Ported LS6 TPiS. You know the combination is the key. The LSXRT isn't always better in some combinations. I have a $1000 LSXRT paper weight as proof. Darth the above applies to your comments saying Jake is spot on when in fact he isn't.

I had it dyno tested. Did you two do that? My statements are based on data collected from testing on my set up. It's not an opinion.

In at least one specific case, like my small cam 383LS1 the Fast LSXRT wasn't as good as a tweaked LS6 intake.

That's why my fast LSXRT is collecting dust on the self in the garage, replaced by a Ported LS6 TPiS.

 

Exactly, your combinations were just too wrong to take advantage of the LSXRT.

 

Jake said you have to cam it differently. I don't believe he is disagreeing with you.

Hammer really is stuck on the FAST being better on every combination. I will never be of that mind set. I could very mulch see better air speed in the LS6 making more power on a smaller motor/cam vs the FAST's greater volume. Some will argue the only place air speed matters is in the head runner but I believe high air speed in the intake is going to make for higher speed heading into the combustion chamber.

 

LOL. By that way of thinking, if you ain't top fuel you ain't ****. I would much rather have power down low for most street driven applications. My current weekend toy is 228/230 cammed (smallish) and it isn't as much fun in most instances than my 216/220 combo. It will walk the **** out of it in the 1/8th and way worse in the 1/4 but still not as much fun for the 3-4 second throttle blips I often enjoy.

 

You have insults. I have actual test data

I'm sure the MSD wouldn't have worked well for my set up either. Properly marching parts is key.

​​​​​I'm happy with 442rwtq & 465 rwhp and the area under the curve the small cam 383 LS1 made. Drives like stock

​​​​​I've provided my input based actual direct experience using an LSXRT intake and the tuning issues that occurred to try to help the OP. I have a good idea what the OP has been dealing with - it sucks. One day do another build with a 400+ Cid motor to see if I can get some use out of my old LSXRT.

I will stay out of the thread from here on to help get it back on track so the OP can get some help with the LSXRT issues.
​​​

 

Think if i was having that much trouble with the fast i would sell it and invest in a ported Trailblazer SS intake.... don't let the price fool you eithier. Richard ( Hot Rod magazine) tested 20 LS intakes and the TBSS intake stomped alot of those aftermarket high dollar intakes.

 

Still can't get my injectors to seal with this intake. 4 of the 8 injectors have a vacuum leak. I've pulled them out again replaced o-rings, tried bending the rail brackets, and still the same problem. I've called fast and they're no help. I'm getting ready to start over. What intakes are comperable the the lsxrt that isn't junk? I can't have a vehicle that won't idle!

 

I believe Blackbird has already recommended the LS6 with TPIS mod and port work.