FRPP TVS w/2.8 Pulley on a 08KR - do I need an idler?

[mfield2a]

So, I am installing a (NOS) 660hp FRPP on my ‘08 KR.  For lots of reasons I’m going with this set-up, but mainly because it’s about as “plug & play” and “period correct” for the KR as you can get.  (Any pulley smaller than a 2.8 on a TVS and the KR Tune would probably have to go - and other changes made as well)

Those keeping score may recall the 660hp TVS kit was “technically” for the 2010, and came with a 2.8 pulley (vs the 605hp kit for 07-08 which had a 3.0).  The 660hp “technically” did not fit the 07-09 because it came with an air inlet resontor eliminator, and not the full CAI.  None of that matters on a KR, all you need is the blower.  

Here is the one snag I can’t seem to find the answer:  Supposedly the 660hp bolts right onto the 2010 with no need to change the belt or put on an idler.  I can’t find much info if installing a 2.8 pulley on a 07-09 requires the 90mm idler or shorter belt.
 

Revan Racing has 84” listed for this set-up recommended, which sounds right considering the stock belt is 84 7/8” (for 07-12).  

Anyone have experience with this?  I’m trying to figure out is do I need to go down to a 84” belt OR go to a 90mm idler when going to a 2.8 pulley - or neither?  (PS - I’m really not interested putting on any idler arm.)

Any helpful info would be much appreciated!  

Edited December 25, 2019 by mfield2a

[NorthSnake]

Not sure if you need a shorter belt or pulley, however I can tell you for certain the the "KR tune" with stock supercharger and intake will NOT suffice with NOS FRPP 2.3 TVS (605 or 660 hp). The kits came with a Refundable/Returnable Ford programmer used to update the tune(Specific to vehicle ECM number) and IIRC they had a CARB sticker for emissions certification.

[mfield2a]

3 hours ago, NorthSnake said:

Not sure if you need a shorter belt or pulley, however I can tell you for certain the the "KR tune" with stock supercharger and intake will NOT suffice with NOS FRPP 2.3 TVS (605 or 660 hp). The kits came with a Refundable/Returnable Ford programmer used to update the tune(Specific to vehicle ECM number) and IIRC they had a CARB sticker for emissions certification.

Thanks for the reply.  So the subject of KR tune working with the FFRP TVS and TB has been beaten to death on the KR section. There have been a few running the set-up for years now with no issues, (Keep In mind only a handful of KR’s are running this set-up so the pool is small) More importantly quite a bit of data was shared to support this.

That said, I come to forums for a reason: to get and when I can provide useful information.  It’s been a couple of years since any real new information has surfaced around this, but if you have some personal knowledge or first hand experience with the KR Tune with the FFRP TVS I would be much appreciative to hear more.   

As for the idler I did get from VMP a 2.8 is in tolerance for the stock set-up.

Edited January 10, 2020 by mfield2a

[NorthSnake]

I actually have the full 2010 FRPP TVS kit (used on my 2009 GT500 vert), including the Ford Racing "Pro Cal tool" used to update the tune. You can always try it with just the "KR tune" and see what happens if you want to risk it. I would certainly have it checked on a dyno with Air Fuel readings before any kind of throttle on the street is applied. Its just cheap insurance, keep in mind that our cars do not have the large safe range of built in computer tuning that later models (2011?+) have with knock sensors etc.

The kit did not require a tensioner or anything as far as I recall. I might have the instructions somewhere or you could look it up online using the old Ford Racing part number and see what was included in the kit, if no belt or tensioner you have your answer. 😃 I bought my full kit used from a guy upgrading his SuperSnake to a larger Whipple years ago.

 

Anyhow I really can't see how the KR tune could adapt properly for the 2.3 TVS vs the factory Eaton. As far as I can see the KR tune has a slightly higher airflow range to account for the 45?ish HP gained from the CAI and ported KR hood. The TVS adds considerably more air and hence far more power even at the original base kit levels than even the KR of at least 100hp (not WHP though) .

I long ago changed to a 2.5 pulley (required auxilliary tensioner), vmp 67 throttle body and elbow, injectors etc, hand ported the TVS etc and it dynos 654 WHP at 91 octane with VMP tune.

 

Not sure if any of this helps, more of a "be cautious" post than anything else. Cheaping out on a tune or a dyno run can cost mega $$$ if assumptions or internet "heresay" are wrong.

 

Cheers! From way up north!

[twobjshelbys]

You could go to the detailed parts breakdown and check the part number for the idler pulley on both vehicles...

As general guidance if you put a smaller pulley somewhere you need a larger one somewhere else to compensate.  Sometimes the standard idler/tensioner can take up the slack.  But you run the risk of belt slap or tossing the belt if there is too much of a difference. 

Edited January 10, 2020 by twobjshelbys

[mfield2a]

Thanks for the replies.

So it’s not being cheap, it’s a matter of looking to keep the MAF curve untouched (if possible). Almost all “over the counter tunes” start to mess with that table.  All those tunes are looking to get max HP out of the engine.   I’m not looking to put down max power in this car.

The pro-cal tune that came with the kit is 99% identical maps to the KR tune, with the exception that the KR tune accounts for the lower back pressure of the KR exhaust.  

That said, I will be taking the car in for a custom dyno evaluation and if needed update to the tune. Until then, Running cooler plug and 93 octane (keeping off WOT) won’t be an issue.

 

More to come!

[me32]

Anyone get the final answer for this?

[mfield2a]

Went with a stock 2013 belt, took out timing at WOT. Added a touch of fuel at mid and WOT.  She barks great now!