Fuel pressure regulator boost reference from the pipe

TWARD700 · Apr 1, 2012

My sled runs great wot for about 20 seconds till it feels like it runs out of fuel or some thing pop pretty good to. Running 10 lbs of boost 5k 330 jets had the power jets 2.5 turns out pulls great 1250 EGT then goes to 1350 after 20 seconds or so. What is all involved in doing the fuel pressure reference from the pipe? Thanks

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swrev · Apr 1, 2012

I welded on an extra layer of metal to gain some more material. Drilled and tapped it. I used steel braided brake line. Hardest part was finding a fitting attach to the regulator for me. Pretty basic install. Then all you have to do is readjust base fuel fuel pressure.

Here is a pic of mine where I attached to the pipe.

swrev · Apr 1, 2012

oops, wrong pic

TWARD700 · Apr 1, 2012

What did you have to adjust you base fuel pressure to?

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swrev · Apr 1, 2012

Running 3-4. I may try and go lower yet just to see how it works. Sled used to work best w/ 5-6 before changing reference. Been running 10 lbs all winter w/out any top end fueling issues. Could only run 8 before w/ out having fuel problems.

TWARD700 · Apr 2, 2012

What are you seeing for fuel pressure at 10 lbs of boost? When I look down I see 10 lbs of fuel pressure at 9 lbs of boost

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swrev · Apr 2, 2012

16-17. Base fuel, boost, and addition 3-4 seems to be where it runs off the pipe. I thought pipe reference was good for about 2 additional lbs, so I was really happy seeing around twice that. You should be seeing your boost plus your base pressure w/ your setup if you are pulling off charge box or carbs. I never ran mine off the charge box, but off the carbs, it seemed like I got a little better fuel shuttoff than I do off the pipe, but overall, I am much happier w/ current setup. No more starving for fuel under boost. Shortened the rod to the wastegate yesterday and added some springs to the pipes, going to run 12 or so tomorrow. Currently have mine adjusted so 8 lbs is as low as I can run, but seem to be able to only add 4 or so w/ the boost controller. Might have to see if I am getting a boost leak if I don't get more boost out of it tomorrow.

gus bohne · Apr 2, 2012

What you get is the exact amount of exhaust backpressure added to your base + boost..

so the example of say 10 psi boost, 3 psi base fuel press. and total of 16 psi fuel pressure would mean an exh. backpressure of 3 psi over boost .

That changes as boost increases too, when using smaller turbines you see it shoot the fuel pressure up to say 25 psi on a 17 psi boost tune on same sled. meaning your getting into detoooooo land real quick at that point in your boost range so its time to BACK it off !!!

its an opportunity to see the range your turbo sizing is safe in, as well as gain some margin in fuel delivery. using this method you can drop base to 2 psi if you want..

Playing in the 5 psi over boost or more range is dangerous for the long pull rider. stay in the 5 or less window..

Gus
swrev, thanks for filling the man in. You certainly have your head around your turbo exceptionally well..

swrev · Apr 2, 2012

Thanks Gus, means alot. You've given the carb turbo sleds a ton of knowledge to use. Even w/ all of the Doo's out there, I still had about a dozen people say to me that they didn't think you could turbo a Skidoo, let alone a carb sled. Keep up the good work.

swrev · Apr 2, 2012

gus bohne said:
so the example of say 10 psi boost, 3 psi base fuel press. and total of 16 psi fuel pressure would mean an exh. backpressure of 3 psi over boost .

That changes as boost increases too, when using smaller turbines you see it shoot the fuel pressure up to say 25 psi on a 17 psi boost tune on same sled. meaning your getting into detoooooo land real quick at that point in your boost range so its time to BACK it off !!!

That's good to know, going to run 12-13lbs tomorrow. Running a 2860 on my sled. I'll watch for fuel pressure spikes.

Bendy · Apr 2, 2012

So...

you're saying too much fuel increases exhaust back pressure, which in turn raises combustion temperatures?

gus bohne · Apr 2, 2012

No Bendy not possible.. you missunderstood.

the amount of back pressure is turbo sizing dependant.. so a smaller turbo will have higher back pressure that will get even higher as boost increases do to its physical LACK of flow.

this increase WILL show on the fuel pressure gauge so YOU can see when you're getting into the limits of flow from any Turbo...

its an added benefit to using pipe reference, you get to see the rise above your boost + base and use it to determine exact pipe pressure..simple.

Its been a life saver for the e tech turbos Ive helped make live and stop murdering reeds...But On the ETECH I have a trademark to prevent others from copying it. on any kit ...:usa2::usa2::usa2:

Gus

sw rev, you will see when its getting scary... bet its around 13 ish under 5000 feet.. saw it @ DTR..U still gain power till 10 ish above boost but dome errosion on the exh edge happens too often even for drags..
Imagine the friggin heat..!!

Let us know how the ride goes please.. its mx time out here and I do miss the sound of a turbo.. thank god the kids are still on 85's and superminis. I get my fix of mrx01 stink @!!!!!

TWARD700 · Apr 3, 2012

Thanks for all the info what size braided line did you go with 1/8,1/4,3/8? Is the hose all stainless or does it have rubber/ plastic liner.

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gus bohne · Apr 3, 2012

the hose is braid over either rubber or teflon lined. Nitrous feed line is teflon lined.
You can also use copper tube, or just plain old fuel line on barbs.

If you look at a KTM 65 cc mx bike you will see THEY use nothing more a piece of 1/4 inch rubber fuel line with worm clamps !!! the heat you think is there,, is not anywhere near as hot as one would believe.

have a great remainder of the season man..

swrev · Apr 4, 2012

Tward-I used the steel braided because I like the look of it. Believe it was 3/16 ID.

Gus-Highest I saw my fuel pressure hit was 18-19 lbs; boost, 12-13. The conditions were so icy that I didn't get a chance to really see what I was going to run consistently. It could get "western" in a hurry. Even glancing at egt's was a little nerve racking, if they weren't flashing I didn't pay attention. My fuel pressure guage only goes to twenty, so it will be hard for me to see what the amount of back pressure I am getting out of my setup if I go any higher on the boost. We were riding 7-8000' most of the day.

gus bohne · Apr 4, 2012

Your in good shape at those numbers.. close to the edge but still not there..

Once you get past 5 psi over boost your in race fuel only territory..

Since I made 1 single change to the recipe last trip to dtr we saw some friggin amazing ****...

Over the summer the RACE to 1000 hp is going to heat up. expect the first 800hp sled by july..it will be a triple...muhahahha !!

Thats my nostadamus prediction.. 5, 4 cyl 2000 cc turbos are in the worx..cat,doo and 2 polaris...

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Fuel pressure regulator boost reference from the pipe

TWARD700

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TWARD700

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