Cant get WOT throttle down to 11.9

[kinger]

I played with the GEMS all week long trying different settings and I still cant get 11.9 on a WOT run. It goes to 12.5 then climbs to 13.5 before I let off. Haven't been able to hold it to the bar for longer then a few seconds.

Its a MPI stage 1 shimmed running 10-13psi it seems to jump higher then 11psi as well. So much happening going that fast I didn't even get the rpms I was running.

When I increased the mode 4 for boost accelerator if just made it pig rich in the midrange and when I'm going down the trail at 9-10 psi with light throttle (say 70mph). I was running afrs from below 10:1 to up to 13.6:1 at different loads and the sled never skipped a beat didn't seem to make much difference.

I also got around 11-12mpg the whole time.

Do I need the fuel pump or is it the GEMS?

 

[DC5]

If you are running a stock fuel pump it is not keeping up. They start dropping fuel pressure at around 7lbs near sea level.

 

[DC5]

I am running the same setup as you but using RB3. I mounted a walbro fuel pump in the stock location.

 

[SPEED]

Kinger, What Dc5 said , if your running that boost you NEED a bigger pump, you are running out of fuel on the top, I did the same pump on my S/C to solve problem at lower elevations (Look at my dyno runs on Dyno-Tech)
You will spike more boost then should settle down to 11 lbs. Also do not over-rev (the s/c charger at that level of boost is on the outside edge of efficiency)

 

[kinger]

What is the part number on that pump? It replaces the stocker and works ok?

 

[DC5]

Ebay item number 280416304818. I got my pump from Speed and it was mounted on the stock pump mount with tie wraps which probably would work fine but I ride in northern quebec where I am 300 miles from civilization so I made a solid aluminum mount to make sure it held together. If you search you can find pics of Speed's mount. Here is a pic of the stock pump.

 

[SledFreak]

Are you still running the stock fuel pump without the external an fuel pump? I was speaking with Heith from MPI yerterday and he said even at 7psi, you need to run an external fuel pump...

 

[kinger]

I have never had luck with a walboro pump in any vehicals i have had to modify the stock pump housing.

I would love to have a external pump in conjuntion with the stocker, is that what MPI reccomends? I will have to call them and see what they offer.

Thanks for all the help guys.

 

[mbarryracing]

My FPP setup has an external (secondary) pump inline with the OEM in-tank pump with stock injectors and this setup has been to over 21 lbs boost without running out of fuel according to AFR's.

 

[DC5]

Walbro pump works well and can support almost 400hp. You will have to modify your pump housing but imo having 1 fuel pump is a better solution than adding a second inline pump. Also cheaper and easier to tune.

 

[kinger]

I guess I should restate my question I can get the fuel closer at WOT 12.2- 12.4 AFR but then the mid range is super rich (10:1), still a fuel pump issue?

Thanks guys

 

[TT]

Get a OEM fuel pump removal kit from MCX or powderlites and use an external fuel pump (Whalbro GLS392 or MSD-2225)

Powderlites fuel pump removal kit:

MCX fuel pump removal kit:

 

[kinger]

Thanks TT and everyone! I called MPI and they agree its a fuel pump issue. Its a bummer because I saw speeds post and asked Ulmer about it this summer when he had my sled but he never had to put one in, mine is a 06 so maybe its tired. Oh well.

Now to decide on internal or external...

 

[DC5]

I have a powderlites fuel pump delete kit and an external msd pump if you want to buy it. I bought it and never used it.

 

[Skydog]

Yes guys i feel every boosted sled needs to upgrade the hole fuel pump, step one to a boost build!!

Skydog