ISR Mod Caution: Warped FPR PVC end cap due to over-tightening *Please Read*
09-16-2003, 07:15 AM
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ISR Mod Caution: Warped FPR PVC end cap due to over-tightening *Please Read*
I pay very close attention to how my rig runs, and for the past few days, it was just a little rough. So yesterday I popped to hood to check things over and I found the FPR ISR end cap slightly warped. There are two reasons this happened:
1. I over-tightened the SCH40 PVC end cap clamp.
2. Heat soak caused the end cap to conform to the clamp and its shape, which exerts pressure in an egg shape.
Why is this bad? Well, the end cap was “swimming” in the intake hose – slightly. That allowed a small amount of “undocumented” air (by-passed the MAFS) to sneak by. This in turn caused a very slight roughness to the engine. To the average person, this may have gone unnoticed. But for an anal freak like myself, it was a big deal. My biggest concern was unfiltered air getting through. Glad I caught it.
Here is the piece I am talking about. This same caution also applies to the 98’s.
Granted I live in PHX, so you may never experience this, but it is something you may want to keep an eye on. If this continues to be a problem, I am going to find an alternative method.
Bottom line:
Do not over-tighten the clamp to the PVC end caps. Yes, even SCH40 PVC can warp.
Here is an illustration of the problem:
1. I over-tightened the SCH40 PVC end cap clamp.
2. Heat soak caused the end cap to conform to the clamp and its shape, which exerts pressure in an egg shape.
Why is this bad? Well, the end cap was “swimming” in the intake hose – slightly. That allowed a small amount of “undocumented” air (by-passed the MAFS) to sneak by. This in turn caused a very slight roughness to the engine. To the average person, this may have gone unnoticed. But for an anal freak like myself, it was a big deal. My biggest concern was unfiltered air getting through. Glad I caught it.
Here is the piece I am talking about. This same caution also applies to the 98’s.
Granted I live in PHX, so you may never experience this, but it is something you may want to keep an eye on. If this continues to be a problem, I am going to find an alternative method.
Bottom line:
Do not over-tighten the clamp to the PVC end caps. Yes, even SCH40 PVC can warp.
Here is an illustration of the problem:
09-16-2003, 07:31 AM
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I figured it out. The problem is that the end cap is slightly too small. That creates the need for the clamp to be tightened to the point where it is out of round (egg shaped).
The fix is to add diameter to the end-cap, which in turn will keep the clamp in a circle.
For now, I added duct tape. In the future I will find a more permanent fix.
I will definitely keep you all posted.
The fix is to add diameter to the end-cap, which in turn will keep the clamp in a circle.
For now, I added duct tape. In the future I will find a more permanent fix.
I will definitely keep you all posted.
09-16-2003, 11:31 AM
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Sticky for a bit, sure! Sticky forever: no. 
If people are looking for ISR mod info, I'm pretty sure they'll end up finding this thread anyhow.
Al
P.S. It'd be a good idea if Corey or Dr.Z, or someone, added a link to this thread in the tech write-up. Or add "a word of caution" note at the end of it to this effect.
If people are looking for ISR mod info, I'm pretty sure they'll end up finding this thread anyhow.Al
P.S. It'd be a good idea if Corey or Dr.Z, or someone, added a link to this thread in the tech write-up. Or add "a word of caution" note at the end of it to this effect.
Last edited by HBoss; 09-16-2003 at 11:33 AM.
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09-16-2003, 11:49 AM
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you may want to try SCH 80 PVC - same ID, but larger OD than the same thing in SCH 40 - higher resistance to heat also. i use it alot in idustrial applications
my .02
my .02
09-18-2003, 06:04 AM
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Actually, it all has to do with the type of clamp you use. The stock clamp exerts too much pressure on each side of the PVC, causing it to warp under extreme heat.
A 2" radiator hose clamp should solve everything. That will exert pressure the whole way around. Replacing my warped PVC and getting a 2" hose clamp is my next move.
A 2" radiator hose clamp should solve everything. That will exert pressure the whole way around. Replacing my warped PVC and getting a 2" hose clamp is my next move.
Last edited by rimpainter.com; 09-18-2003 at 01:06 PM.
09-19-2003, 05:26 AM
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96 runner beat me to it..I did the ISR mod just last w/e and I really don't like the design of the hose clamps Toy uses, although esthetically they look better than the band type clamps. Call me picky, but I prefer function over looks (in my autos, that is !!).
So when I went by Lowes to pick up a 1" PVC female end cap, I got a 2" ribbon type hose clamp...I must say the preformance has improved...
my .02
So when I went by Lowes to pick up a 1" PVC female end cap, I got a 2" ribbon type hose clamp...I must say the preformance has improved...
my .02
Fix found!
09-28-2003, 06:48 PM
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FYI to anyone who hasn't checked this out!
My ISR mod setup has been in my truck for several months now. I re-set mine to Christian's write-up just about a week before Christian noticed this problem. I took mine out about a week later with the new and improved method.
I took a look at my old cap earlier today and noticed a major warp. 2 weeks is all it took - and this is in the overcast mornings we've had here in San Diego.
If you haven't looked at it yet you better do so quickly.
My ISR mod setup has been in my truck for several months now. I re-set mine to Christian's write-up just about a week before Christian noticed this problem. I took mine out about a week later with the new and improved method.
I took a look at my old cap earlier today and noticed a major warp. 2 weeks is all it took - and this is in the overcast mornings we've had here in San Diego.
If you haven't looked at it yet you better do so quickly.
09-29-2003, 04:40 AM
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Peter, what did you have in there and what did you fix it with. Ours ('03 3.4) looks like all we need is a 1" female end cap. I used a hose clamp at the start, replacing the Toy one. I just looked this am and have not noticed any warpage but it has only been about 2 weeks now. But I would like to be prepared if it does start.
Thnx.
Thnx.
