10-11 lbs boost, 8:1 vortech fmu, walbro fuel pump, sard fpr set at 38 psi idle.


I'm hitting 81 psi at full boost near redline... I'm missing around 20 psi of fp.... I'm clueless on this one.... I'm detonating, and my fuel filter is new... i dont know what to do.

 

i tried messing with the walbro to make sure there were no fuel leaks in the line.... now my idle flips back and forth from like 26-28 psi RAPIDLY.

When I boost, it takes a few seconds for the lines to build pressure...

I'm thinking my fuel pump is shot.... anyone know the warrenty on these things?

 

All I know is I had the reverse problem where the walbro intake wouldnt get me anymore than 50psi max of FP. Then all the sudden one day 1month later, it started cranking out 100psi and still is cranking it out. So I got no clue whats the issues on these pumps.

Dixit

 

There must have been something stuck in the tube or it was twisted. Then when you went wot it got untangled

 

How do you know you're detonating? What's your EGT?

How about going to a 10:1 disk?

 

egt's don't really go above 1200ish since I'm only not having enough fuel above around 5500 rpm or so. Plug are coppery with silvery, white specs.


What's got me wondering is why the fp is fluctuating like that.... and now I can't go above 45-50 psi :-/

 

do you mind to show me a picture of your plug?

about your EGT, 1200 @ full boost near redline? that's low. even I partial boost @ 5psi from 80 to 100mph, the EGT raises to 1430F.

 

sorry, can't take pics... but it's definately detonating.... and the detonation explains why the egt's are so low.


I pulled the walbro and was making sure the lines and plugs were ok....

I'm thinking the pump is on its way out. The fp is still wandering rapidly from 26-28 psi... and at half throttle, fp shoots up to 80 psi, and i can hear the walbro running.... so that eliminates the guage being the problem.

I already talked to Jaime at PTI and he's willing to warrenty it out, I just wanted to make sure that it is the pump itself...

I suppose i'll swap in the oem one this weekend and see if that cures the wandering fp.... if so, i'll trade the walbro... if it isn't the problem, **** it, im selling the sc

 

I thought detonation made higher EGTs....?

I'm probably just ignorant.

 

High EGT is an indication that the afr is lean. A lean mixture can lead to detonation, especially in boosted engines. Once detonation begins, however, the EGT will go down because heat is being transferred from the exhaust gases to the piston crowns and cylinder heads.

In the absence of detonation there is a boundary layer between the exhaust gases and the piston and cylinder head surfaces that acts as a thermal barrier to the exhaust gas temperature. The explosive nature of detonation breaks through and disperses this boundary layer, causing the heat in the exhaust gases to diffuse into the piston and cylinder head.

 

Sweet....I totally understand now.

Thanks for the write-up.

 

Question: What is this boundary layer made up of?

Question 2: So know one knows what my fuel issue is?

 

Wild guess. Check the voltages to the fuel pump??

 

well didn't have a voltemeter...

I switched the oem fuel pump back in... the crazy fp flipping quit... but now i can't adjust my fp with the sard... damn.



Edit: FP was turned up WAY too high, so it didn't look like i could adjust it.... but after loosening the nut, it did indeed go back down.... thank god!


So I'm only out like 5 bucks to cover s/h for a new walbro pump.....

 

so would it be fine if i run a walbro with no aux fuel pump that came with the vortech and use a 8:1 fmu????
then how would i know how much fuel pressure i have??? would i still need a fpr to go along with the vortech fmu???

 

since i'm not boosting.... the fmu doesn't do anything.

 

Sorry to take so long answering this, I was out on vacation all last week.

A boundary layer is made up of the same gas or fluid that is flowing through the pipe. The difference being that the boundary layer is a thin layer of the fluid that stays attached to the surface of the pipe and is characterized by laminar flow through its thickness. Have you ever noticed that the water at the shore of a fast flowing stream moves at a slower velocity than in the center of the stream? That is what is going on in the boundary layer.

From an engineering viewpoint, the boundary layer is where shear forces are present in the moving liquid because there exists a velocity gradient, with the fluid or gas closest to the pipe surface having zero velocity. The velocity increases over the thickness of the boundary layer until the maximum fluid velocity occurs at some distance away from the surface. At that point the flow changes from laminar to turbulent if the flow is fast enough.

Since the boundary layer is characterized by laminar flow with zero velocity at the pipe surface, the boundary layer acts as a thermal insulator and heat transfer from the moving fluid to the pipe is greatly diminished. That is one reason why an aluminum piston with a melting point of around 600C can survive in a combustion chamber where exhaust gas temperatures can routinely get up over 800C. If something happens to disrupt the boundary layer thickness or flow characteristics, then the heat transfer can be greatly increased, which is what happens during detonation.