Tim's 944LS1 track car build!

Engine is back together and runs well, off to the dyno on Thursday.

You do anything like bump the compression, port the heads, etc?

docwyte wrote:You do anything like bump the compression, port the heads, etc?

No, just a stock rebuild. Not looking to add power as I don't need it for my race class (ST3 9:1 wt/hp).

Good news is that the rebuild turned out well, the car spent time on the dyno last night. We were not able to increase the peak HP (from initial build), but we did get 25 ft lbs more torque as well as 20 more rwhp down low (2700 to 5500 rpms). The area under the curve increased considerably. I would have liked a bit more on the top end (20 rwhp) but we just can't coax it from the stock engine without making it want to explode. As is, we still have a very safe engine.

I'm going to put it on the track a few times before deciding whether I need to change the cam and springs.

Nice Tim! Area under the curve is good. A small mod like an LS6 intake could get you that 20 rwhp.

Rich

Doubt the ls6 manifold will add that much, maybe 10rwhp. A FAST92/92 combo would add 20rwhp tho

Spent yesterday at Talladega Grand Prix for a test and tune. Engine pulls really well with the new found torque.

The last few events I've had an issue with the car bogging on hard right handers. At first I thought that was related to fuel starvation due to low fuel in the tank. Now I do not think that is the case as it was bogging with lots of fuel in the tank. It only happens on hard right hand turns and does feel like fuel starvation but I guess it could be electrical as well.

My plan is to replace the fuel pump (Welbro 392; i have a spare in the garage) and fuel filter as well as check all fuel lines and electrical. Got to get this sorted as I'm racing at Road Atlanta in 8 days!

Odd. There are a couple of ideas here:

[You must be registered and logged in to see this link.]

The story at the bottom from M758 is interesting. There's a float in the filler neck to prevent spillage that had cracked and dropped into the tank. This caused fuel starvation in right handers.

Good luck.

Rich

I hope it's that simple, thanks for the link!

Pulled the sender, all is fine with the tank internally. Will replace the filter and pump.

After spending the last hour searching and reading, it is just as likely that the issue is electrical, so will look there tomorrow morning.

The starter wire was burnt to the metal and was able to move side to side quite a bit. I'm thinking it was grounding itself on the y-pipe. At least that's one possibility but without some track time, there's no way to know.

So that grounding would reduce voltage, inhibit good spark and reduce power? That's a good smoking gun, hope that was it.

Rich

Still planning on changing out the fuel pump and filter. If it goes away, I won't know the actual cause, but then again, I won't care

Not a good race weekend for me, I was fighting the "fuel starvation" issue all weekend it is worse. I have changed out the fuel pump, fuel filter/regulator, removed the in tank filter, and added a ford starter solenoid to eliminate power going to the starter. At this point, I'm lost as to what is causing the problem.

Starvation started occurring after half a lap when you peg the throttle. Does not matter if you are in a straight line for coming out of a corner. It only occurs under load, does not happen when in neutral.

Guess I'll try to get it on the dyno this week and see if we can figure this out while we are recording data.

Any chance the wiring to the pump is damaged or corroded? Being a problem under load, it has to be on the supply side of the fuel system. Check the fuel pump ground and power for damage. Another possibility is a pinched fuel hardline. I've seen that on tracked cars a few times and it shows up as an odd miss under load.

That sucks. A pressure gauge at the fuel rail will help with diags on the dyno.

Rich

I did check all the lines and none are pinched. Have good pressure (60 lbs) when checked at idle and when revved, but do not know the condition under load.

Tell me if I'm thinking clearly on this.

1. Fuel pump runs at maximum flow when engine is running, regardless of rpm or load. Thus, the same quantity of fuel is always being delivered to the regulator.
2. The regulator/filter controls how much is sent to the fuel rail based on the back pressure in that line (so under idle, most fuel goes into the recirculation line).
3. Flow rate of the pump is affected by two main items, pressure in the system and power to the pump.

Have you checked the injectors? Are they stock or old or been sitting for years? Check the plugs too. How did you come to fuel being the problem again?

Can't be sure that it is either fuel or electrical at this point. Injectors were cleaned 1.5 years ago. Will pull plugs tonight.

Theyre probably fine but checking things the plugs may help you see if its running lean (fuel fault) or rich (Ign. fault).

Weve also seen faulty intake systems here. I cant remember who it was but their intake tubing was weak and collapsing under load.

You may also want to run dedicated grounds to the block and heads.

Dont worry, Youll find the problem!

Pulled the plugs, they look great.

Intake is pretty solid, doubt that is an issue but will watch it on dyno.

I've got two grounds to the block and one to the passenger side head.

Will go over all grounds in car tomorrow, tonight I promised to help a friend corner balance his 911 race car (I have a lift and scales, that means lots of friends!).

Lemming wrote:(I have a lift and scales, that means lots of friends!).

You Bet!

I've cleaned and checked all grounds as well as looking over all fuel lines. Cleaned up some of my wiring off of the kill switch now that the new Ford external starter solenoid is attached. I've added a voltmeter as well. Will be at Barber instructing (I do the beginner classrooms as well as check rides for the Alabama PCA), so I can test this weekend. The only problem is that I don't have snow tires for the car and we are to get snow on Saturday

Where is the regulator getting the vac from? If that line becomes pinched or damaged it will screw with fuel flow. If it isn't getting enough vac signal it will reduce the amount of fuel. Didn't see it mentioned but it may be worth a look. Also try using a vac tester to see if it is holding vac. If it can't hold vac then it will bleed off and not hold pressure on WOT.

I've seen too enough vac leads coming from the same area, pinched hoses, holes accidentally cut/torn into the hose during install and even one end that somebody forgot to attach.