Progress Thread Progress Thread- From6to8's 1994 Cobra Supercharger install

[from6to8]

Okay so went and got the car dyno tuned a few weeks ago and it made 403/392. The tuner said that more than likely at 200k miles he felt more than like the oil is getting past the rains and skewing the AF because when he made adjustments and the timing and I think fuel pressure there was not a decent jump in hp. His opinion was that it was best to be safe and keep everything at a nice safe level and I know at some point I know he was at only 23° of total timing and he said he was going to make a few adjustments and see if the numbers jumped pretty good and it did not.

So anyway I felt pretty good and everything and was about to leave and put the car on the trailer and I should have that should have been a little bit of a red flag right there because when I went to leave the parking lot to go to the next parking lot it's kind of bald a little bit on taking off and didn't really think much of it so just got it on the trailer and got it home. I drove it the next day and overall it did pretty good it felt decent but I noticed I Little Miss I thought it was just in 5th gear around 60 to 70 mph but even if I downshifted to 4th and still had a little miss. About a week went by before I drove it again for the second time and I was about to take it on a nice hour and some change trip and it's still did the same thing with upon taking off having like a bog hesitation kind of jerk and then it just exploded so I knew something was going on.

Got it home and I was like well let me check everything out you know check the distributor cap wrote a button check the wires and stuff just make sure there was was nothing glaring or anything. When I called the tuner he said send it back to him and he'll make a few changes he said it's probably I think he said it's probably lean on startup so he was going to make some changes. I sent the chip to him and got it back plugged everything up and drove the car and everything felt a whole lot better. The only thing I noticed now is the fuel pressure which was at 33 to 35 with the vacuum line on is now about 23 to 25 with the vacuum line on. I'm probably just going to go ahead and bump the fuel pressure up today and just see how the car feels see how it responds and I'm going to call him in the morning to see what he thinks rather it's you need to make another adjustment in the tune or what..

He didn't mention anything about the 255 pump we're running out of fuel & I do have 60 lb injectors. Doing a little research right now on supercharger combos with a 255 pump and for what I'm reading so far into my little bit of researching started at 10 minutes ago it seems the 255 should be good up to 750 crank HP.

The air fuel is reading between odd I'd say 13.5 to about 14.5 on the gauge

@Noobz347. @AeroCoupe

 

[AeroCoupe]

Is your pump a high pressure unit? Remember that setting your fuel pressure to 39 psi the pump actually has to over come the boost pressure as well so it needs to be able to put up 49 psi which is right at the limit of the standard 255 lph Walbro. Mostly what I am seeing is 500-600 fwhp for a 255 lph pump.

If the pressure was 39 psi when it was tuned and it’s now less than that you need to correct the pressure. For example, I upgraded my fuel system and had the injectors cleans so I set the fuel pressure at 39 psi and it was a turd and did not want to run. Bumped it back up to 46 psi (where the tuner set it) and it ran like it was supposed to.

Noobz is waaaay more experienced with boost so listen to him.

 

[from6to8]

Is your pump a high pressure unit? Remember that setting your fuel pressure to 39 psi the pump actually has to over come the boost pressure as well so it needs to be able to put up 49 psi which is right at the limit of the standard 255 lph Walbro. Mostly what I am seeing is 500-600 fwhp for a 255 lph pump.

If the pressure was 39 psi when it was tuned and it’s now less than that you need to correct the pressure. For example, I upgraded my fuel system and had the injectors cleans so I set the fuel pressure at 39 psi and it was a turd and did not want to run. Bumped it back up to 46 psi (where the tuner set it) and it ran like it was supposed to.

Noobz is waaaay more experienced with boost so listen to him.

yes it is .

Is that in your experience or from reading what others have said too. It seems the 255 should be from some stuff I've read should be good to 750 crank hp but I'm sure with boost yeah i guess maybe 6 ish , 6 something. Waiting on @Noobz347 input for sure too and I'm going to call the tuner in the morning to see what he thinks but I'm going to bump it back up and see what she does.

 

[Noobz347]

The only real difference between the 255L and the 255L HP is the high pressure pump's ability to resist fall-off at elevated fuel pressures.

So, I don't think you're running out of fuel as the result of the pump.

The fuel pressure just automagically changing from one moment to the next is suspect to me. I mean... Once you've set it, that should be it unless your idle is unstable. I would keep an eye on this and ensure that fuel pressure is not drifting.

403/392 is pretty damn good for that setup.

Also: Keep an eye ball on fuel pressure when you're just driving around from light to light. You should not see big swings in pressure as you're operating the gas pedal. If you do, this could indicate an issue with feed power to the pump (product of our old OEM electrical systems).

 

[Noobz347]

Another thought:

I don't think you're picking up oil through the rings. If you're getting oil in the combustion chambers, check the inlet tract for oil. My guess is that if you're getting it, it's coming through the PCV and not the rings.

 

[from6to8]

The only real difference between the 255L and the 255L HP is the high pressure pump's ability to resist fall-off at elevated fuel pressures.

So, I don't think you're running out of fuel as the result of the pump.

The fuel pressure just automagically changing from one moment to the next is suspect to me. I mean... Once you've set it, that should be it unless your idle is unstable. I would keep an eye on this and ensure that fuel pressure is not drifting.

403/392 is pretty damn good for that setup.

Also: Keep an eye ball on fuel pressure when you're just driving around from light to light. You should not see big swings in pressure as you're operating the gas pedal. If you do, this could indicate an issue with feed power to the pump (product of our old OEM electrical systems).

Okay so matter fact I'm just going to it'll be easier to copy my notes instead of remembering exactly everything that I just did with the with starting the car up cold and driving it.

Notes -

Started up on Sunday March 8 and the fuel pressure is 32 at startup, 36 with vac line off. 26 27 cruising down betaw which is the road I live on which is about a 35 mph out in the country. 25 24 25, 22, 23. Fluctuating some between shifts(dropping lower) then back up to what it was, it is increasing as I get into boost, noticed for instance on an 80° day and with the water temperature nearing 210° getting back in the yard a fuel pressure shows 22 so curious as to the IAT temperatures definitely affecting fuel pressure possibly

Also pulled the vacuum line off to see if there was a fuel smell and I didn't smell anything. The fuel pressure regulator I did buy that years ago years and years ago but like I said there's no fuel smell so I'm not suspecting the regulator is necessarily bad I guess or on the way out..

 

[from6to8]

Another thought:

I don't think you're picking up oil through the rings. If you're getting oil in the combustion chambers, check the inlet tract for oil. My guess is that if you're getting it, it's coming through the PCV and not the rings.

I will keep that in mind as to check to see about any oil in the inlet possibly. I don't see any oil or anything or any kind of mist or any evidence of oil in the breather by the way

 

[from6to8]

I did pull the line off the fuel pressure regulator and did not smell any fuel by the way

 

[Noobz347]

Started up on Sunday March 8 and the fuel pressure is 32 at startup, 36 with vac line off. 26 27 cruising down betaw which is the road I live on which is about a 35 mph out in the country. 25 24 25, 22, 23. Fluctuating some between shifts(dropping lower) then back up to what it was, it is increasing as I get into boost, noticed for instance on an 80° day and with the water temperature nearing 210° getting back in the yard a fuel pressure shows 22 so curious as to the IAT temperatures definitely affecting fuel pressure possibly

IAT has nothing at to do with the FP. Only vac does.

Other than that, you account of fuel pressures as you're roaming around, does not look out of place. As you vac goes away, pressure increases until you reach the volume limit of the pump.

You initial post suggest that FPR might be drifting but you will need to monitor to see if that is true.

 

[from6to8]

IAT has nothing at to do with the FP. Only vac does.

Other than that, you account of fuel pressures as you're roaming around, does not look out of place. As you vac goes away, pressure increases until you reach the volume limit of the pump.

You initial post suggest that FPR might be drifting but you will need to monitor to see if that is true.

Gotcha. I will mention those numbers and everything I just said to you I will relay that to the tuner in the morning and see what he thinks. I do know I need to get a small clamp and put on the VAC line from the regulator to the T on the throttle body even though it's nice and secure. By the way I ran it without a clamp on my NA setup prior but just for peace of mind I will put a clamp on it.

It doesn't sound or seem like that's the issue of why the numbers are drifting though of because the vacuum line doesn't have a clamp LOL. Even pulling up on it there's very good tension before it wants to come off. Very curious to see what he has to say about the fuel pressure getting that little cruising around town at what I've seen at 21 but the good thing is at least under more throttle pressure it does increase.

 

[Noobz347]

A Vac leak to the FPR could cause it.

How is that line plumbed? Is it sharing the vacuum source with any other components?

 

[from6to8]

A Vac leak to the FPR could cause it.

How is that line plumbed? Is it sharing the vacuum source with any other components?

I have the boost vacuum sensor going to the T fitting thing on the throttle body. So on that t fitting thing it is the big line coming off the vacuum tree, the fuel pressure regulator, as well as the boost vacuum sensor that I recently added before the supercharger installed

 

[from6to8]

Then the vacuum line coming off of the supercharger bypass valve is going to the back of the upper intake

 

[Noobz347]

I have the boost vacuum sensor going to the T fitting thing on the throttle body. So on that t fitting thing it is the big line coming off the vacuum tree, the fuel pressure regulator, as well as the boost vacuum sensor that I recently added before the supercharger installed

Try separating those. The line to the FPR is small. It's not capable of much air volume. Small changes in that line can have an effect of the FPR.

What is this boost/vacuum sensor for? What is it feeding?

 

[from6to8]

Try separating those. The line to the FPR is small. It's not capable of much air volume. Small changes in that line can have an effect of the FPR.

What is this boost/vacuum sensor for? What is it feeding?

They're on separate ports of the T just so you know. The and I don't even know if it's really a t but I see them on a lot of cars with an oem elbow setup where it's a fitting that has about three vacuum ports so it maybe it's called something different. So in essence the vacuum line is going to one port and the other two are going to the other two ports so do you still think I need to move the boost vacuum sensor? It is for the dual boost vacuum wide and air fuel

 

[Noobz347]

Post a pic

 

[from6to8]

Post a pic

The big line that you don't see a hose on yet it gets that biggest line from the vacuum tree

 

[Noobz347]

I still can't tell what's what.

Here's what I think I've picked up from your description:

From the vacuum tree, you're going to a line and then a T and then off to the FPR and Boost Sensor... Is this correct?


If so, you [should] come off of the vacuum tree and go straight to the FPR with nothing else fed from that line.

 

[from6to8]

I still can't tell what's what.

Here's what I think I've picked up from your description:

From the vacuum tree, you're going to a line and then a T and then off to the FPR and Boost Sensor... Is this correct?


If so, you [should] come off of the vacuum tree and go straight to the FPR with nothing else fed from that line.

Okay I just googled an image of the elbow adapter that has that screw in fitting that has ports for vacuum. The biggest Port gets the biggest vacuum line coming off of the vacuum tree. The other two ports are for the fuel pressure regulator and now the boost vacuum sensor. Prior to the boost vacuum sensor that port was capped. So they are all getting vacuum at that adapter which is after the throttle body.

 

[Noobz347]

Ok... That does seem to be as it should be.

I just didn't want you teeing off a quarter inch line to two components at the same time. You're going right to the source which should be totally fine.