Project Shoehorn - M90 into a 4.0L

[SolarBell]

So at this point the project is as complete as it's going to be. I'm going to be keeping my eye out for T-Bird M90's to rebuild and swap in, but until then I'm just going to run it since it runs fine otherwise. I'm not going to get a final dyno run until I can source a new compressor and have it rebuilt (preferably with coated rotors) to reach max pressure and performance.

 

[Talyn]

Have you thought about having the rotors gun drilled to reduce weight since it will be out?

 

[SolarBell]

I have a question for those that understand fluid dynamics far better than I.

The intake manifold for my supercharger looks like this:



And as you can see here, the air goes in the side of it through the throttle body, then it has to go down and out the side to enter the compressor.



It's not super clear, but you can see the throttle body port on the left and the top of the intake to the compressor at the bottom center.



Here's the big question - since the manifold is completely square and the port to the compressor is basically on the bottom side corner, what are the chances that the corners and other bits are causing vortices and turbulence that might cause stalling and starvation of flows entering the compressor? I know that turbulence in high flow air manifolds can cause issues, just see the redesign of the 99+ intake manifold. I've also read about systems that reach a maximum sonic speed on certain intake designs. The manifold is 4"x3"x3/16" square tube that is about 10.5" tall with a 30* cut on the top to clear the A/C lines. The port to the compressor is about as far to the bottom and side as I can make it. Would this cause enough turbulence to have problems? Would it be worthwhile to design an build a new manifold that is entirely rounded and smooth to the airflow?

Any thoughts? I'd like to investigate this line of potential performance impact before I go down the route of completely replacing / rebuilding a new compressor.

 

[O-Gauge Steamer]

To be honest here, I have looked at this just about every way I can and about the only thing that might make a difference would be a floor, set at an angle to direct the flow into the compressor's intake port. But then, the vacuum ports are lost so, not a good idea that.

Looking at the flow path, it makes two 90 degree turns in a relatively small area. Not the end of the world to be sure as I have seen installations that were way more convoluted than this one. This is, IMO, a rather elegant solution to the issue...

I am not convinced that this is the source of the lack of boost either. IMO.... It is far and away more likely that the compressor has lost it's close tolerances and the extra gaps are the root cause of the performance issue.

Unfortunately, we do not have a spare compressor to fit in order to check the hypothesis.

This installation is about as tight as can be done. Given where the compressor's intake port is located, I am at somewhat of a loss to see a ready alternative.

By the numbers, this should be making the same amount of boost I am getting out of my much smaller compressor.

Just my opinion here, but this is a fine example of fabrication given the space restrictions.

Unless one is willing to sacrifice their A/C compressor, room to fit under the hood is hard to come by...

I know that I sound like I am standing on a soap box but....
Used compressors are a throw of the dice. That being the case, I recently came across a NOS M90 that was originally built for the Jaguar 4 litre. A brand New Compressor that, unfortunately, would not fit into SolarBell's installation. Otherwise, it would be there making lovely boost.

It does have a vehicle to go into though.

More to follow in a dedicated thread by SolarBell and myself.

In summary then, I do not believe that this intake manifold is the root cause as, comparatively speaking, it is very straight forward in design and fabrication.

I have personally observed one, not to be named, individual that used 90 degree castings that took a 3" diameter opening ans squashed it down into a 3" x 1" shaped opening. He used 3 of them on a Land Rover Discovery. And that compressor managed to build boost although...

It ran so hot that is destroyed itself in less than a month of daily driving. Bearing failure.

Heat is always the enemy and an overly restrictive intake (which this is not any where near being...) will cause the compressor to work in order to breathe. It was by removing the intake restriction on my Sprintex installation that I was able to increase the boost from 5 pounds to 8.

The original design had a great deal (>3Hg) of residual vacuum in the compressor's intake at WOT. This manifold does not. To me, at any rate, this indicates a no restriction condition which is a very good thing indeed.

 

[Hypoid]

The original design had a great deal (>3Hg) of residual vacuum in the compressor's intake at WOT. This manifold does not. To me, at any rate, this indicates a no restriction condition which is a very good thing indeed.

Word! Wisdom from the era of carburetors, and still valid.

 

[O-Gauge Steamer]

You bet it is valid. Any restriction in the intake is power lost. It becomes more important in a Supercharged installation as the compressor WILL OVERHEAT as it works.

It only makes sense if you think about it. The last thing you need/want/desire is to choke off an intake. IMO, the biggest advantage that a "cold Air Intake" gives is a reduction in resistance.

We all know that they do not provide "cold air" unless they take outside air and all of the piping is insulated...

 

[kastein]

What donor was your SC from?

I will see if I can find one locally. At least a decent condition junkyard one could be used to verify whether or not you have an issue here and keep you rolling while the other is out being rebuilt.

 

[SolarBell]

It came out of a '89 - '92 Ford Thunderbird SC.

If it isn't a problem with my compressor intake manifold then my compressor is suspect. It had some scoring on the housing walls which I didn't think were significant at the time and couldn't see when I purchased. There was some crud in the rotors and housing which looks like it ingested some some oil and debris at some point (or more than one point). I thought I could get away with it.

I'm getting 5 psi now but should be getting about double that with the pulley I'm currently running. I tested my residual vacuum with the intake disconnected and got a near-zero reading. I get some residual with the intake and filter attached but that part is as optimized as it's going to get for now.

 

[yossarian19]

Well, unless you have a vacuum / pressure leak it has to be the pump, right?
But what about a vac / pressure leak?

 

[SolarBell]

If there is a leak I can't find it and I've looked more than once. And I pull a serious vacuum - around 13 in/hg at idle and 18 in/hg if I let off the throttle headed downhill. That's around 2.5 PSIa at my altitude.

 

[O-Gauge Steamer]

The "high" vacuum that SolarBell sees at idle indicates, to me at any rate, that the plumbing connections from the TB to the cylinder head are, all of them, sound. If there were a leak, I suspect that it would not be able to develop the vacuum.

By "high" I mean that he is getting near perfect vacuum readings for this altitude. Unlike folk living at sea level who can expect to see 21" Hg at idle, we lose a minimum of 1" HG per 1,000 foot altitude owing to the Mean Air Density. And, current barometric pressure plays a larger part up here than down there. I took data from my F/IC every day for a year to establish just what the "average" day here in the Springs is with regards to the ambient PSIa (pounds Per Square Inch, Absolute). What the average reported was 12.5 PSIa as opposed to the 14.7 PSIa at sea level.

This is just a simple fact of life and is the reason that we also cannot make the same amount of boost as an identically equipped vehicle at sea level. I would pick up an "additional" 1.6 pounds of boost if I were at sea level. 8 here, 9.6 there...

You just can not compress what is not there...

As another data point, my engine idles around the 10" Hg point and I see up to 15" Hg during engine overruns. All told, a 3" Hg differential across the board between mine and his. My engine does not consume much in the way of oil to speak of being less than 1/2 quart between changes.

But then again, SolarBell's engine has less miles on it than mine does and that is the difference...

"Ideal" Idle Vacuum levels:
Sea Level 21" Hg
Mile High 15" Hg
Here (6.4k') 14" Hg

Actual performance will vary based upon the number of miles on the particular engine and the Camshaft that is being ran. High lift, long duration Cams do not allow the engine to develop good vacuum at idle owing to the valve overlap. In extreme cases, the engine can not make enough vacuum to operate the power brakes but must have an external pump installed.

This I know from direct experience...

 

[SolarBell]

Note for all the people finding this on Google. On further testing, the V8 WJ IAC motor is completely electrically compatible with the XJ IAC. No swapping of pintles required.

 

[Talyn]

Is the plug the same as well?

 

[SolarBell]

Yep. Plug and play.

 

[Milner]

Bringing this back up. How is it running today? I am very interested in doing a similar project! What would you do different if you had to do it again?

 

[lazyxj]

Bringing this back up. How is it running today? I am very interested in doing a similar project! What would you do different if you had to do it again?

Any updates?
Is it still running ?

 

[SolarBell]

Any updates?
Is it still running ?

My current daily driver is technically a forced induction inline 6 turning about 330 horsepower. But it's a Cummins 6.7 in a Ram 2500 with about 800 ft-lbs of torque.

It's not running, but not because of the supercharger setup. Last spring I started overhauling the suspension to clean it up and rebuild it, but I never really finished and the XJ has been hover-driveway art ever since. (My son started racing motocross the summer and I didn't realize the time commitment) As soon as it gets warm for a few days I'm not already busy I'll be getting it back together.

One item of note - If you are doing this, don't cheap out. I did the eBay special oil separator and ended up having to dump it and put in a Moroso because the eBay one failed.

 

[SolarBell]

So, to resurrect this whole thing.

This thing has basically sat in hibernation for the last 2 years ever since I bought my Ram truck. I'm bringing it back to life.

I'm back to issues with the AEM FIC/6. All of my older versions of the AEM software fail out with the ever-so-helpful "Unexpected Error", and the only available version of the software (which works) requires a newer FIC firmware version. The newest firmware version is known to cause tuning problems. What to do...

 

[rav]

SCT tune it with flyinryan

 

[Boostwerks.com]

SCT tune it with flyinryan

I would have to recommend this as well, or Chris tuned. I was able to get my FIC setup working fine for the most part, but it still had the typical draw backs of a piggy back system (lean throttle tip-in, super rich cold starts...ect).

Or shell out some coin for a decent standalone. I've been really impressed with the new stuff from Haltech fwiw.