Some of you may recall this thread regarding the performance data on the ISR mod. In summary, I found the ISR mod to provide huge performance gains for the money, with the FPR line hooked up (uncapped).

There has been some discussion about whether or not to cap off the FPR vacuum line. Dr Z has found that by capping off the FPR line, the air/fuel ratio is richer. This provides less of a chance for pinging, and with proper tuning, better performance at high RPM at WOT. So, I decided to cap it off, and have another go at a 30-70MPH, 3rd gear, WOT test run. The test data is surprising:

1st Run: 11.92 sec
2nd Run: 12.02 sec

Capped AVG ET: 11.97
FPR line hooked up (uncapped) AVG ET: 11.66

The FPR line capped:


After a brief email discussion with Dr Z, we feel the loss in performance is caused by a rich condition at lower RPM's at WOT.

So, in my particular test, which lugs the engine at the start (2K RPM), there is a loss of performance. So, with proper tuning, or for the drag racer, the capped FPR line would work nicely. However, if you run a similar set-up as myself, where tuning is limited, then you may want to keep the line hooked up. Your call.

 

Where did you get that cap to replace the silencer? I'm considering doing this mod. Do you really recommend it?

Thanks.

 

I actually got the cap from my uncle, who had a plumbing end cap sitting around. You can go to Lowes, or any plumbing store, and find the correct end cap for your application. Just take off the IS in the parking lot, and bring it in.

I totally recommend this mod. And obviously, I recommend the FPR line hooked up.

Gaining almost .2 seconds from 30-70MPH for free (or for the cost of an end cap) is WELL worth it. Keep in mind, you should run premium fuel with this mod.

My 4Runner definetly pulls harder. Its also really loud at WOT around 4 - 5K RPM, the only drawback next to using premium fuel in my opinion.

 

Interesting Post!! Did you happen to notice any pinging with either the vaccuum line plugged or unplugged. I would like to do the ISR but the premium gas would put me in the poor house. :pat:

 

No, I did not notice pinging with the FPR line capped or uncapped. So, for me, premium fuel is a necessity.

On my 98 Taco, I noticed pinging while running 87 Octane. I am not taking any chances with my 96.

Here is a pic of the FPR line hooked up (my current set-up)

 

hey man i have been reading all about these upgrades. what exactly did you use for everything, including idameters and lenghts if you can. and where you got it. sorry for any inconvinence

 

All of the numbers are in the "official" writeup here on YotaTech:

https://www.yotatech.com/~corey/tech...ntake/dr_z.htm

As for getting the parts, you should be able to find them at a home center store like Lowe's or Home Depot. Personally, I got mine at Home Depot.


Have fun!

Mark

 

This ISR mod, does it work w/ SuperCharged Runners as well?
anyone have any specs regarding this?

 

Hey FWIW- I put the silencer containing the vacuum line nipple back on, reconnected the vacuum tube, and noticed a pretty significant increase in performance over "capped."
I still had the other two silencers removed and the deckplate out. So, guess I need to rig a vacuum nipple to a plumbing endcap now!

Just some more qualitative data to support 96's numbers.