Horsepower fetish.

[Tabcon]

I have been seriously considering the Moss supercharger for my build. I've put a great deal of time, effort and money into the engine build and I expect my engine to dyno at about 165 hp, but considering the amount of time, effort and money I've put into it, it seems like a low number to me. If Moss's claims are correct, installing the supercharger should give me an additional 75hp +/-. This would take me to about 240hp. I like this number much better.

I'd like to know more about the characteristics of using a supercharger on my engine. It would be nice if I could see a dyno graph. Does anyone have any idea what the power band would be with the supercharger? Does the power come on at a certain RPM or is it a wide power band?

With the new chassis and the improvements I have made to the drive train and the suspension, I have no doubt the car can handle much more than 165 horses and it almost seems like a waste not to realize some more horses from my engine.

 

[tdskip]

+/- 50% gain over stock ain't bad Tab...

I'd be worried that what you did to get it to this level won't like much boost...

 

[swift6]

The base build of a supercharged engine is different than a performance naturally aspirated engine. For continuity why don't you list the characteristics of your current performance build to get to a projected 165hp. My base suspicion is that if you added a supercharger to your current build it wouldn't last very long and would NOT produce an extra 75 horspower. Many things such as your current compression ratio, camshaft profile etc... things that boost power on a normally aspirated engine are detrimental to performance of a forced induction engine.

I mentioned this in the other thread as well.

 

[justin_mercier]

Superchargers do not like high compression ratios so if you shaved your head for a higher compression ratio, you probably wont get much good use from a super charger, and in fact could just cause more problems than it's worth.

 

[Tabcon]

Interesting. Thanks I had no idea about this. If this is the case, Moss really needs to revise the ad they have for the supercharger.

"<span style="font-weight: bold">Combined with additional engine modifications</span>, you can have race engine power, but with a big broad torque curve and none of the "peakiness" one expects from a wild race camshaft."

What mods are they referring to if not performance mods?

 

[NutmegCT]

Interesting. Thanks I had no idea about this. If this is the case, Moss really needs to revise the ad they have for the supercharger.

"<span style="font-weight: bold">Combined with additional engine modifications</span>, you can have race engine power, but with a big broad torque curve and none of the "peakiness" one expects from a wild race camshaft."

What mods are they referring to if not performance mods?

Tab, I'm betting the mods they refer to are the alterations needed to install and run the unit. Note what Moss says on their own website:

<span style="font-style: italic">"Please note: These kits are designed to be installed on engines that are in good condition with the original compression ratio and correctly operating distributor and fuel system. Increased compression due to block or head modification, worn distributor components, or a weak fuel pump can contribute to damaging detonation under load. "</span>

Tom

 

[Tabcon]

Unfortunately, that makes sense.

My head has been milled to run about 10.5:1 compression. What is the CR for the original engine?

So now my option would be to buy a new head for $3k, then a supercharger for $4k.
For $7K, I think a better option for me would be to install a custom built high performance 4 cylinder like the ones Esslinger Engineering builds.

Their 2.5 liter is about $8k without any induction system, but I can use my Weber set up for it. I will try my engine first to see how it performs. It may be great, but more horsepower is always a good thing.

My current TR engine has:

-89mm liners

-forged J&E short deck pistons

-lengthened Pauter rods

-nitrided and balanced crank

-Fidenza aluminum flywheel

-Integral Stage II camshaft

-2 Weber 45 DCOE's

-fast road/race stainless headers from Racestorations,

-Pertronix HP pointless distributor

-Pertonix 65,000 volt high output coil

- the head has been ported, flowed, cc'd and the combustion chambers enlarged. It also has over sized stainless valves and it was milled to 10.5:1 CR.

Kas Kastner helped me with the build and told me that I should get at least 165hp out of it, possibly a little more. Since I have never actually driven a TR4 with 165hp, I can't say if I think it will be enough or not. I'm sure it would be plenty for a stock frame and suspension, but with the new Ratco frame and all the chassis modifications I have made, I have no doubt the car could handle 250hp with no problem. Actually, I'm certain it could handle much more than that. Maybe I should just toss a 302 in...lol.

 

[booley]

what you did to get it to this level won't like much boost...

check with the guy that did the work on your cylinder head, you guys must have agreed on what compression ratio you were going to end up with. what kind of gas were you planning on using? he could probably tell you if there is any "room for boost" in your combination. i'm pretty sure the work you did to the bottom end could handle the power. a "little boost" would give you gobs of torque...but you'll probably end up running race gas.

 

[Tabcon]

The compression ratio is 10.5:1

I can use pump gas, but premium only.

If stock compression was about 9:1, I doubt that a little more as in my case would be that big of a deal. If I were running 12 or 13:1, then yes, I can see where I may have a problem.

In any event, I could easily lower the compression to 9.0:1 by having a thicker head gasket made. Since I need a new head gasket anyway, this is most likely the best solution to my craving for horsepower.

 

[justin_mercier]

TR6 stock compression ratio is 9.5 for the European Petrol Injection engines, but stock compression ratio for the carburated engines is only around 8.0.

 

[Darrell_Walker]

Hi Tab,

I'm considering the supercharger for my car, too. I guess I'm pretty much committed, since I sold my Weber setup.

Anyway, the stock compression ratio for a TR4A is 9:1. My car is about 9.25:1, which I think is going to be OK, but if not, I'll install a thicker head gasket. But on Moss's TR6 supercharger page, they have a dyno run with a 9.5:1 engine, so I'm pretty sure I'm OK. I don't know about 10.5:1.

In the reading I've done, anything you can do to help the exhaust side is good, since the supercharger doesn't help with that. The big benefit of the supercharger is overcoming any problems on the intake side. As far as your cam, I think you want to avoid too much overlap, since you would end up pushing the fuel right through.

 

[Tabcon]

I should be good on the exhaust side with the headers and all the head work that was done. I also have dual exhaust with free flow racing mufflers. I'm not concerned with compression as I can pretty much adjust that to whatever works best.

I wish I could talk with someone who has installed one of these things though. I'm very curious about the performance. Also, do you think you could run a Weber instead of an SU for induction?

 

[Darrell_Walker]

Also, do you think you could run a Weber instead of an SU for induction?

I'm sure you could, though you would have to have a manifold to adapt, and assuming there is clearance. Actually, the hot setup might be to use one of the TBI adapters and set it up with fuel injection.

 

[John_Mc]

TR6 stock compression ratio is 9.5 for the European Petrol Injection engines, but stock compression ratio for the carburated engines is only around 8.0.

I understand the earlier TR6s had higher compression engines, or at least I was told my 71 has the high compression engine (head). Is this true? and what is the difference in the CR between higher compression engines and regular?

 

[swift6]

The OPs car is a TR4 but TR6s bagan with 8.5:1 CR and then eventually dropped to 7.75:1 due to emissions concerns.

This is for the carb equipped US TR6s.

 

[swift6]

Anyway, the stock compression ratio for a TR4A is 9:1. My car is about 9.25:1, which I think is going to be OK, but if not, I'll install a thicker head gasket. But on Moss's TR6 supercharger page, they have a dyno run with a 9.5:1 engine, so I'm pretty sure I'm OK. I don't know about 10.5:1.

You could also stay with the lower CR and go with the big boost kit for more power.

 

[swift6]

The compression ratio is 10.5:1

I can use pump gas, but premium only.

If stock compression was about 9:1, I doubt that a little more as in my case would be that big of a deal. If I were running 12 or 13:1, then yes, I can see where I may have a problem.

A 1.5 point increase in compression is much larger than it sounds. Especially when it comes to controlling the flame front in the combustion cycle in order to contol any pre-ignition. Modern cars handle the variation in fuels and manage CRs of 10:1 and higher through sophisticated engine sensors and spark control.

 

[Tabcon]

Also, do you think you could run a Weber instead of an SU for induction?

I'm sure you could, though you would have to have a manifold to adapt, and assuming there is clearance. Actually, the hot setup might be to use one of the TBI adapters and set it up with fuel injection.

Excellent idea!

Since I'm not at all familiar with supercharging, I'm going to do some research on it and see what shakes out. Fuel injection does sound like the best method of induction though.

 

[Tabcon]

I called Moss today and spoke with someone there who seemed to know a great deal about their new supercharger kit. I'll pass on what he told me on to anyone who may be interested in installing one.

<span style="font-weight: bold">Compression</span>

Not a problem up to 10.0:1 CR

<span style="font-weight: bold">Camshaft</span>

Not a problem unless it is a race or borderline race cam. A mild to moderate cam does not present any problems and as a matter of fact, the TR4 they have installed the kit on has a mild camshaft.

I also spoke with the manufacturer of the supercharger, Magnuson, and they said that using fuel injection with the supercharger is good mainly due to the fact that you can make finer adjustments to the mixture and volume.

I created a spreadsheet to calculate what my compression ratio is currently, and it turns out to be 10.81:1. By replacing my head gasket with one that is 0.059" thick (the thickest offered by Cometic) my compression would fall to 9.8:1, which puts me in range. The copper gasket I have now is only .019" thick.

I'm going to go ahead and do the modification as soon as I move. Oh yea, I'm moving to Dallas next week. The cost of the Moss unit per horsepower is cheaper than what my engine build turned out to be, so I think it's not such a bad deal after all!

I'm not exactly sure how much effect on current horsepower lowering the CR will have, but if it drops from an estimated 165hp to 150hp, the addition of the supercharger should give me an additional 60hp making the total number come to 210hp.
According to the handy dandy 0-60 calculator, this equates to a 0 to 60 time of about 4.5 seconds. Not bad for a tractor engine!

 

[SkinnedKnuckles]

Cool - a good mod that I wished I'd have done. Just start scoping out replacement pistons....