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:

 

Nice catch!!!!!

 

yea definitly a good find Christian. I'm gonna take a look at mine tonight.

 

Wow, thats really something...

Good thing you caught it sooner rather than later. Any idea on what you are gonna use for an alternative?

 

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.

 

Mods:

Can we make this a sticky?

If not, I understand. I think current and future ISR modders should know about this...

your call of course.

 

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.

 

Thanks Al.

 

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

 

Great idea, thanks Nate.

I will check the plumbing supply store for that!

 

I had the same thing happen but with just the main tube of PVC for mine.

Link Here

 

It looks to me like you could use a large metal freeze plug instead of the pvc. No warpage. Mabey?

 

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.

 

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

 

Glad you like it! Good idea too!

 

I JUST re-did my ISR with your specs too, Christian
I do have some extra hose clamps so I'll probably use that. Thansk for the looking out!

 

Please see this thread for a permanent fix.

 

Like I said, thanks for the looking out

 

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.

 

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.