Personally I do not think the cams are the wrong ones. The later closing should be more than made up for by boost.
I reflect back on the 2.6 turbo. To me the engine is real lazy till you get past 13lbs boost, then it becomes very happy. Granted I have not driven a stock one since 1988. and turbo boost numbers are not the same a supercharger numbers as far as boost settings.

Your torque curve is as flat as can be. Not a particularly wide powerband but that may be the torque converter not allowing the low end to show or just the way superchargers are being it is not providing enough boost down low. You made a comment that you did not feel you wanted more boost down low but from what I see the engine wants it. When I set up turbos I make sure they get full boost by 2500 revs and keep up till way past the power peak, If it is a stock engine I want the boost in below that. Your setup looks to lack the bottom boost and then dies quick after 5000 unless that was lifting off the throttle. I would expect to have full boost in by 1800 on your engine. Is your supercharger big enough? Sounds like you have it spun to the recomended max now. As far as bottom pulley it is easy enough to change the timing tab.

Now I did a tune session a few years ago with Megasquirt on a 4G63 that plain ole did not make power. The numbers looked right but the engine did not pull. That was on the MS1 chip not the MS2 you are working with. That project was put on hold so I do not have resolution yet. Best I can tell it was ignition related, an issue with many installs using wasted spark on the early MS1.The engine is running fine on Emanage still.

Yes, that is indeed a flat torque curve - likely the benefit of the blower.

It's not that I don't want boost down low - I do want it available (and I do have it), but I don't want to have to use it so early as load increases.... and I think that's a function of the power band location..... in turn, a function of the cams. The engine just is not making power on its own down low.

The performance isn't as bad as the numbers appear. The Mustang dynos have a lookup chart for all vehicle models so wind resistance and weight are taken into consideration. The factor for my truck was 22 - the highest number the dyno operator has ever seen.... the old refrigerator on wheels. So, the resulting numbers are downgraded accordingly. I'm no dyno expert, but I'm told that a DynoJet would probably show up to 40HP more. If instead we were looking at 150HP/180TQ + estimated driveline losses raising it to say 180/225, we'd be saying "Wow!" <img src="/forums/images/graemlins/lol.gif" alt="" />

I was concerned that fuel was limiting, so I did watch fuel pressure as the engine spooled up on the dyno.... it started at 43psi, climbed to 60 and held steady.... so that appears to be ok. The next thing I'm going to do is a compression check to make sure the rings are ok.

Meanwhile, I'm calculating LSA and valve overlap on the 24v non-turbo and turbo heads - noticed those cams are tighter than the Diamante or Montero cams... interesting. There's always the option of custom cams, but I'd rather not go down that road.

I'll be in and around Atlanta for the next couple of months...... maybe I can arrange a drag race with one of the locals and see the real world difference. <img src="/forums/images/graemlins/wink.gif" alt="" />

Frank

They might not like getting there ass whooped by an old Montero, I pissed off many with my old Monti coming out of traffic lights. I beat a guy in a chevy pickup once that tried to pass on the right, I had a full 39 Chevy on my trailer and beat him, He drove like an <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> all the way down the road after that.

Frank, some thoughts on supercharger cams at Grape Ape Racing.

Thanks - I've seen that and read it a hundred times before I installed the Diamante cams. They're saying the same thing that Charlie is on the valve timing - and it's what I believed would be the rationale before I made the swap. I'm just not seeing the results on the dyno or my butt gauge. From what they're saying, you'd think I should retard the cams instead of advancing them. It appears that I'm looking at the other side (closing) of the lobe from Charlie (and GrapeApe) and it may be necessary to give more consideration to the entire cam pattern.

According to the dyno operator I used, he has seen many instances where cams that were retarded as much as 8* worked better in a blower application. I suppose it might have to do with how much power the engine can make on its own and where you want the power band to be. Certainly, some of the engine's power is lost to turn the blower... if the engine doesn't quickly make power on its own, it can't get going with the blower.... but that's a completely different issue that I'm not complaining about. It doesn't sap engine power if the blower isn't on line because of the bypass valve, so I think there should be more power built lower and before the blower ever comes on line for ordinary street driving. That means an earlier closing intake and less valve overlap. That may be one reason the cam doctors use a different profile for blower engines.

I've spent a bunch of time building a Mitsubishi cam spec table - perhaps it should be in a separate thread for future reference, but I find it very interesting that for the 3000GT TT, Mitsubishi did some of the things mentioned by GrapeApe (late valve opening times), but they reduced valve overlap by shortening the duration time on both intake and exhaust to different extents.

It appears to me that any of the N/A cams will be a compromise and the best solution might be custom cam patterns - or changing to the 24v DOHC heads where I can have separate control over the intake and exhaust cams. But changing the heads will also require a change to another ignition system - not impossible w/MS, but probably not a lot of fun.

If anyone can tell me how to convert an Excel file to .jpg or .jpeg, I'll post the chart.

Frank

There is some good information here:

Engine Design for Superchargers

While a lot of what is said agrees with the generally accepted design ideas, there are some caveats that I find interesting and perhaps appropriate for street and truck application that go against the racing standards - some excerpts:







I can see why there is a different cam profile for blowers, but it does appear that the profiles can be quite different depending on what you want the blower to do..... and where you want it done.... and those quoted statements are in agreement with my curiosity and concerns.

It would be very nice to remove the front timing covers, install a set of vernier-marked adjustable cam sprockets and go back to the dyno for a day of cam timing trials.... but I'll need to machine the sprocket plates first.... maybe someday.

Frank

With Stony's help, maybe this will work:



I can add additional camshafts to the list and post it as a separate thread.

Frank

I was thinking some on your comments about the lack of low end power. Keep in mind that you built a rather short runner intake manifold. This alone will affect your power curve. The manifold is not short enough to not affect the curve but to short to provide low end power.

If I recall your comment of the boost being lower than it first was, did you not reduce the compression ratio? The reduced compression also makes more volume to fill. The air passing through the engine will be equal or greater than previous but the net affect with a positive displacement blower is a lower boost number. With a positive displacement blower boost is a measure of air not getting into the engine.
So with a bit more cam, some porting work and lower compression your airflow has been increased. Now you need to get the blower to give you more air.

Yes, the runner length is part of it, but I don't think it's the whole story. You'll be surprised when you see the MSQ.

Frank

Compression ratio - OE is 8.9:1 with a 13cc dish. Because I planned to run the Diamante cams with the later closing intake, I had the Wisecos made with a 10cc dish. Static CR is now raised slightly to 9.05:1.

Boost is now the same as before - I have 7psi from off-idle all the way up. The reason I didn't think I had as much now was because initially I was being cautious and not letting the transmission kickdown during early tuning. As long as the rpms are up, I have plenty of boost.

The later closing intake valve in the Diamante cam is why there is less air to compress when the blower is off-line.... also means effective CR is lower than OE.... the net difference considering cam timing and static CR is around .15-.20 dynamic CR less than OE when not in boost.

I agree that if the boost number dropped it could mean that the engine was breathing better - and I think it is. The flat torque curve is probably a combination of the blower, the work I did to the heads and exhaust manifolds and the exhaust system. The dyno graph suggests that the engine is flowing air well.

I'm probably not conveying my driving impression well - with 32" tires, I find the engine operating around 2000rpms a good bit - particularly with around town driving. The torque curve is much later and I'm running out of vacuum before I can get on the power curve, causing the blower to kick in sooner. My seat-of-the-pants feeling is that I need to move the torque curve lower so it can be better used for all-round driving. I'm really not on the curve at most highway speeds in O/D either.... and I can't seem to get to the curve very easily without the blower coming on line because of the transmission shift points.

Initial fuel mileage was terrible - the first tank was 11 mpg. As the tune progressed, it improved to 12 or so. I haven't checked it since the dyno tune, but will have a chance to do so this weekend - hopefully it has improved, but we actually richened the mixture in a few places.

Frank