1970 GTO Version 3.0

[GTO Jack]

I see you piped your steam vent to the back of the water pump. Did GM ever do it this way? On my set up, I was told it must go to the high point of the radiator both for the air to go to the top, and that is the best place for a bit of suction on that line allowing it to work as designed.

[andrewb70]

I see you piped your steam vent to the back of the water pump. Did GM ever do it this way? On my set up, I was told it must go to the high point of the radiator both for the air to go to the top, and that is the best place for a bit of suction on that line allowing it to work as designed.

GM had the steam vent going to a heater hose on the Trailblazers with the 5.3L. I have the Holley mid-mount system and their main water pump casting has provisions for the steam vent to go into the water pump. It is a legitimate place for it.

Anrew

[andrewb70]

Progress has stalled a bit on the GTO, although I managed to take an interesting and useful detour. I was working with a local customer a couple of weeks ago and I noticed that his 5.4L Mustang GT500 engine had a very interesting looking sensor on the fuel rail. After some digging around I figured out that it is Bosch 0 261 230 093. What caught my eye is that one side of the sensor was in the rail while the other side had a vacuum nipple on it.

As I suspected this is a differential pressure (Delta P) sensor. It outputs the difference between rail pressure and manifold pressure (positive or negative).

You may wonder why we should care. I am glad you asked, because differential fuel pressure is actually what we really care about, not rail pressure. Another way to think of the differential pressure is the pressure across the injector discharge. Let's do an example:

Let's say you have a fuel system that is set to 60psi at the rail and there is no vacuum or boost reference on the regulator, or the regulator is not adjustable. This is a fairly common scenario with a LS swap, simple in-tank pump, and a Corvette style regulator. Let's also say that you have a moderate performance cam and the engine idle around 50kPa, which is about 15in/Hg, which is also about -7psi. Note that the units are all different, but they are describing the same thing, which is the amount of vacuum in the intake manifold when the engine is running.

In this scenario the rail pressure doesn't change, but what happens to the pressure across the injector discharge when the engine is running? Because of the vacuum that is generated by the engine, the differential pressure across the injectors is actually 67psi. In other words, the injectors act as if they flowed more. That is exactly what this sensor will read, because it measures differential pressure directly.

Consider a different scenario. Turbocharged engine, adjustable regulator with a vacuum line hooked up to it. Let's assume the same base pressure of 60psi. When the engine is running under the same conditions, a normal pressure sensor would show 53psi at the rail, but this sensor will still read true differential pressure, which in this case is 60psi. Take the same scenario under boost. Engine is making 10psi, rail pressure sensor will be reading 70psi, and this sensor will still read 60psi. The purpose of having a vacuum/boost referenced fuel system is in fact to maintain consistent differential fuel pressure.

This is a fun topic and if anyone has any questions, please post them.

Here is sensor mount that Vic machined.











It attaches right to the back of the rail with the AN-6 female to female union.



The eagle eyed will notice that it is mounted to the Cougar. I am using the Cougar to do the testing for the sensor.

Andrew

[wfo guy]

Good topic.

[sccacuda]

I don't totally understand why Ford would use this sensor. I know Chrysler and GM use a rail pressure sensor and then reference the MAP reading to calculate effective (differential) pressure for either pump speed, pulse width, or both. Any idea why the are using a combo sensor? Does the 5.4 not have a dedicated MAP sensor?

[ryeguy2006a]

That's a very cool sensor Andrew! I'm curious what you will do with this data though? I don't have a lot of tuning experience, but wouldn't any discrepancy in the varying fuel pressures be accounted for with VE table adjustments? Or if you were using the pressureworx module this sensor become just extra data?

[andrewb70]

Progress on the GTO is a little slow, but moving along. I need to thank my friends at The DriveShaft Shop for making me a bullet proof, dual CV, carbon fiber driveshaft.



Here you can see the details of the 108mm non plunging CV and the carbon fiber tube.



This is their new design 8 bolt non-plunging CV. These are used on the Nissan GTR 2500+hp driveshafts. Good enough for this pile...



Here you can see how it fits between the exhaust. There is plenty of clearance, so heat should not be a concern. Besides, there is a constant stream of air passing under the car while it is moving, which cools the exhaust.



Plenty of stick-out for any little movement from the rear end articulation and deflection.



Andrew

[Josh@Ridetech]

Fancy!

[andrewb70]

Fancy!

That's how I roll...LOL

Andrew

[Way2qwk4u]

Looking good. Be ready for the fall cruise weather?

[BlackHD]

That looks great Andrew!

Is the dual cv driveshaft that's on your cougar still a good choice for us less fancy people? lol

[cpd004]

What are some advantages of CV over traditional? I would guess no U joint=less chance of vibration?

[andrewb70]

Looking good. Be ready for the fall cruise weather?

Probably not. Things are moving too slowly to have it on the road this year, especially with the work that I am doing to the Cougar at the moment....

Andrew

- - - Updated - - -

What are some advantages of CV over traditional? I would guess no U joint=less chance of vibration?

Using CVs on both ends makes driveline angles mostly irrelevant and yes, they run very smoothly at high speeds.

Andrew

[langleylad]

Consider a different scenario. Turbocharged engine, adjustable regulator with a vacuum line hooked up to it. Let's assume the same base pressure of 60psi. When the engine is running under the same conditions, a normal pressure sensor would show 53psi at the rail, but this sensor will still read true differential pressure, which in this case is 60psi. Take the same scenario under boost. Engine is making 10psi, rail pressure sensor will be reading 70psi, and this sensor will still read 60psi. The purpose of having a vacuum/boost referenced fuel system is in fact to maintain consistent differential fuel pressure.



Andrew

Thanks for explaining this Andrew , as I'm very much a novice at this I found this info helpful. As I was checking out a data log recently I noticed that my fuel pressure at the regulator was 60lbs and the fuel rail pressure was 53lbs I thought there might be a problem but apparently not . Win !

[Motown 454]

Those CV joints look really stout. The intake looks good all bolted in.

[andrewb70]

Progress on the GTO has been slow, but it is still moving forward. Also, keeping two project cars moving forward is not the easiest...

That said, I have a small update on the GTO. A while back you might recall seeing pictures of when I had the GTO hood 3d scanned. The idea was to have a digital representation of the hood so that something could be made for the hole. When I was at LS Fest I met a couple of guys from a company called Reversion Raceworks. They specialize in custom 3D printing project, specifically for cars. I emailed them after the show and decided to work with them to design an insert for the hood.

They did the design work and I also had them print a prototype for fitment purposes. The print was done in PLA and as you can see it has thick layers. This was done to keep the print cheap and fast.















The fit is spot on. It is as if it was made just for this hood...LOL

Now that the insert is done, I am thinking a clear acrylic cover would look pretty cool. My business logo can also be engraved on the bottom of the cover, so it would show through, but the top would be smooth.

What do y'all think?

Andrew

[Jimbo1367]

That’s awesome. Great idea.

[dhutton]

It looks great. What is the cost to have something like that done? I’ve always assumed it is quite high.

Don

[ekmxryda]

Looks great Andrew,
So are you thinking a flat clear plate mounted on the bottom side?
If they gave you the CAD file for the printed part I could build a couple center concepts in Solidworks for you if you want.

[ryeguy2006a]

I really like that idea Andrew! That insert looks fantastic even for a trial fit.