Super charging question.

Leadfoot281

Leadfoot281

What?! Me worry?
My 04 Silver Birch Marauder has a factory 10.1-1 Mechanical Compression ratio. From what I understand, supercharging this motor sounds like a bad idea. Even with intercooling, detonation will be a problem. 2 or 3 lbs of boost, maybe, but 6,7,or 8 psi sounds like a disaster waiting to happen.

Obviously, it must work or these message boards would be lit up with complaints.

So how do people get away with it? Have they lowered their comp. ratios? Do they run race gas? At 7.5psi it should be good for 50% increase in "effective displacement" as well as 50% increase in torque/horsepower since sea level air pressure is 15psi (naturally aspirated) correct? Am I really just nuttier than squirrel poop? What don't I understand? I just need more low end torque. Thanks!
 
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In the days before cars had spohisticated computers and sensors there was some truth to what you are saying.

There are over 150 S/C MM all running over 8 PSI. Timing for some 14*. They are being driven hard and are not blowing up!

My MM has over 100 runs down the 1320. I put an S/C on @ 45K miles. she does not burn a drop of oil or coolant.
 
Lots of information and resources

There are a large number of us on the site who have S/C applications from different vendors on the site. My S/C is a Vortech, centrifugal type, running 10lbs of boost, with many more mods. Dennis Reinhart's first S/C MM.

We have folks with screw type S/C applications from Trilogy, some of whom have done their own installs due to the simple and clear instruction manual.

We have folks that are running Procharger S/C, centrifugal type, there are now several out there.

The Chaplain says to read the threads and to PM people. S/C threads have a way of going bad because we are all very passionate about our cars and our mods. Most of the S/C threads get locked eventually, so enough said.

Regards, -kjs-
 
The low compression rule in supercharging is old hat. That's what people used to tell you(that you cannot run a 10:1 compression ratio with a supercharger) but there are several dozen of us on this board who have supercharged our Marauders (as you've pointed out) without any problem. It's all in the engine tune. With a higher compression engine, the engine tuner (the one who burns the chip that the supercharger kit comes with) has to make sure that the ignition timing advance isn't as much as the stock setting is, and that the air/fuel ratio is made richer than it is from the factory. If those two things are done properly, then you can run the car on 92 or 93 octane pump gas all the time, and run it hard without it detonating. The factory engines with 10:1 compression ratios (like ours have) simply have to be set with less ignition timing advance than an 8:1 compression ratio engine would have to be.


I've put 20,000 hard supercharged miles on my Marauder since I installed the supercharger( it has 31,000 total miles), and I haven't had any problems. It's all about having the proper engine tune. That's the key to a healthy supercharged engine.

There are three types of superchargers (twin-screw, roots, and centrifugal). The Procharger and Vortech ones are centrifugals, and are designed specifically for Marauders, and cannot be beaten for power above 5,000 RPM's. And many board owners here have them, and haven't had any problems. The Trilogy Motorsports supercharger is an Eaton ROOTS supercharger, which is the one that's supplied on the 2003 and 2004 Cobras from the factory, and is in a kit that's also specifically designed for the Marauder just as the centrifugal supercharger kits are, and it can't be beaten for low-end and midrange power in the 2,000-4,000 RPM range, and there's also many board members here who have chosen that one, and also haven't had any problems.

The twin-screw supercharger supplies good power in the entire RPM range, however, there isn't any twin-screw supercharger kit available for Marauders. There's one person on this board ("Effster") who took a twin-screw supercharger kit made for Cobras, and installed it in his Marauder, and it makes great power also, but he had a real challenging time getting it installed since it isn't designed specifically for Marauders, and he told me that it took him quite awhile to get everything right. But he finally did succeed. I hope this helps you.
 
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BillyGman said:
The low compression rule in supercharging is old hat. That's what people used to tell you(that you cannot run a 10:1 compression ratio with a supercharger) but there are several dozen of us on this board who have supercharged our Marauders (as you've pointed out) without any problem. It's all in the engine tune. With a higher compression engine, the engine tuner (the one who burns the chip that the supercharger kit comes with) has to make sure that the ignition timing advance isn't as much as the stock setting is, and that the air/fuel ratio is made richer than it is from the factory. If those two things are done properly, then you can run the car on 92 or 93 octane pump gas all the time, and run it hard without it detonating. The factory engines with 10:1 compression ratios (like ours have) simply have to be set with less ignition timing advance than an 8:1 compression ratio engine would have to be.
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Just so everyone is clear, I'm not picking on Billy on this post. His just amplifies one of the common misconceptions about compression ratios.

You can have all the static compression you want, in this case either 9.8:1 or 10.1:1 depending on the source [and I'm not debating that here], but what everyone fails to report is the DCR or Dynamic Compression Ratio for a given motor.

Huh? DCR? What the heck is that?

DCR is what -really- determines whether or not your motor will run on a particular octane or not. You see, static compression is just the volume of the cylinder compared from Bottom Dead Center (BDC) to Top Dead Center (TDC). DCR also takes into account the cam and where the intake valve actually closes, either Before Bottom Dead Center (BBDC) or After Bottom Dead Center (ABDC). The later the valve closes ABDC reduces the DCR and that is your TRUE compression ratio for determining where pump gas detonates for a given octane. Yes, there are other factors such as head design etc, but you really don't want to go much over 9:1 DCR or you have problems.

Does anyone have the current cam specs for our motors? If so I can calculate the DCR for our stock 4.6's.

When Mac wanted to be able to run lower octane pump gas, he had 3 options: 1. Lowered his compression with dished pistons (his choice and mine if I were to do it) 2. Back out timing (but no guarantee it would not detonate anyway due to DCR, or 3. change cams to delay the intake valve closing for more ABDC.

The order you choose is mainly decided by how you want to operate your motor and what your goals are. But all motors with fixed cam geometry operate under the same principal.

In my case, on the current 351M for my pickup, I built it with a 11.2:1 static and a 10.4 DCR and, you guessed it, it pings like a mo-fo even on 93. Since the internals are all balanced and the pistons already have a 13cc dish, I opted to get a custom ground cam that lowers the DCR and had a pair of lower compression heads so now I'm at 9.5:1 static and 8.2 DCR. Well within the range of running 89 on up in it.

So, maybe this lesson on SCR and DCR will mean very little to everyone. Just be aware that there are many ways to skin a cat and no one way is always right or wrong.

Cheers!

John
 
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My vehicle has not pinged once. The idle is smooth and runs beautifully. These here motors that we have were built to be run at 7,000RPM (not looking for a debate), and with 500 crank horsepower. These ARE STRONG engines.
 
Heck we've seen cars running 12psi here, and kicking a** and taking names all day. All that with factory motors.
 
Detonation

Cam overlap can affect detonation also. More exhaust gas left over in the cumbustion chamber will lower cylinder temperatures and reduce detonation and ping. This is how the E.G.R. system works by reducing cylinder temperatures thus reducing N.O.X. emissions and detonation. If you can add a little more E.G.R duty cycle you could get rid of some lingering detonation instead of pulling additional timing out. Not sure if the tuners allow you to do this.
Mike
 
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"TooManyFord's" post is correct, and I fully agree and also was aware of all of that. So I haven't any disagreement with you John. I didn't see any need to get into all of that due to the fact that "Leadfoot281" need not concern himself with any of that when it comes to supercharging his Marauder since all of those calculations have already been taken care of in the engine tune that comes with the Trilogy kit, and the one that comes with the Reinhart kit also. And time and the number of customers have proven that.

However, I want to make a statement that is merely speculative concerning the the Marauder engine. And I'm speaking specifically about Marauder engines with the factory stock camshafts, and cylinder heads here..... the cylinder pressures of an engine can be greatly reduced (and therefore would yield a considerably lower compression than what the static compression ratio is) only when the choice of camshaft(s) are of a considerably long duration (usually atleast 230 degrees @ .050" lift)because the intake valves on engines with long duration camshafts often must be timed so that they remain open for a longer interval of time which extends well into the bottom or beginning of the compression stroke of each cylinder.As much as the bottom 3rd of the compression stroke! And that is specifically why the cylinder pressures are lowered with some camshafts. It's due to the valve timing events used with longer duration camshafts.

But in most cases, an engine with a cam duration spec that long, will exhibit a rough idle. And since the Marauder engines have a smooth idle, I highly doubt that they came from the factory with camshafts that have anything more than a 228 degree duration @ .050" lift (which usually is equal to or less than 285 degrees of "advertised" duration). I sincerely hope that you and I haven't confused "Leadfoot281" with all of this technical talk (which would be precisely the reason why I chose not to bring this topic up originally in this thread).

I'm not disagreeing with your point about engine compression. I'm merely stating that the reason that I didn't get into all of that is because while being very educational, it likely does NOT apply to "Leadfoot's" question, nor to the factory stock Marauder engine, unless someone intends to use a supercharger that hasn't come with a complete kit that's already been designed specifically for the Marauder engine that also includes a final engine tune like the Trilogy, and Reinhart supercharger kits do. But again, I'm not intending to argue with you. For the most part, your point is well taken. I'm merely explaining to you why I chose not to bring all of that up in this thread. I didn't think that it neccessarily applies to the question that was asked. but I'm sure there's no harm done. ;)
 
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I don't know the theory behind it but mine is supercharged as well and I beat it like a rented mule, no problems - except gas milage
 
stevengerard said:
I don't know the theory behind it but mine is supercharged as well and I beat it like a rented mule, no problems - except gas milage
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There ya go......^a perfect example of the point I was making. And there are many others here. When it comes to supercharging Marauder engines that have the FACTORY STOCK camshafts and cylinder heads, it's all in the engine tune. ;)
 
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Leadfoot281 said:
My 04 Silver Birch Marauder has a factory 10.1-1 Mechanical Compression ratio. From what I understand, supercharging this motor sounds like a bad idea. Even with intercooling, detonation will be a problem. 2 or 3 lbs of boost, maybe, but 6,7,or 8 psi sounds like a disaster waiting to happen.

Obviously, it must work or these message boards would be lit up with complaints.

So how do people get away with it? Have they lowered their comp. ratios? Do they run race gas? At 7.5psi it should be good for 50% increase in "effective displacement" as well as 50% increase in torque/horsepower since sea level air pressure is 15psi (naturally aspirated) correct? Am I really just nuttier than squirrel poop? What don't I understand? I just need more low end torque. Thanks!
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I have seen stock Marauder motors stand up to 14 a PSI but It comes from a efficient after cooler and good tuning, I am convinced to leave the car at 450 RWHP this is my opinion, the vortech water to air unit is as efficient as any supercharger kit I have seen, it comes from a huge Griffin water to air heat exchanger designed to do just that, cool water, and using a large 2.5 gallon water reservoir that limits heat soak. The Vortech air to air kit is also very efficient the Dyno numbers are here and the data log data is also here, later this week I will post all new pictures of the new pipes we have had custom made at Atlanta, there are three complete pipe assemblies to this Vortech air to air kit with only two 90 degree bends other kits have as many as five so I hope this helps some of your questions, keep in mind that any of the three SC kits now being sold on this site are capable of making more power, its you the owner/customer that ultimately determine how much power you want to make.
 
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BillyGman said:
There ya go......^a perfect example of the point I was making. And there are many others here. When it comes to supercharging Marauder engines that have the FACTORY STOCK camshafts and cylinder heads, it's all in the engine tune. ;)
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Boyeeee i wanna say it :mad2: all in due time :cool: ..
 
Great thread!

I really appreciate all the info posted thus far. No, none of it has been too technical for me. I've read Car Craft and Hot Rod since 1989 and have a fair amount of experiance in the world of "hotrodding".

My MM is a really fun and unique vehical. It's also far more complex and "high strung" (281cid and302hp) than anything else I've ever owned. Grenading a 351W or a 200 I6 is one thing, while grenading this DOHC jewel is another. Therefore, I would like to head into this venture with as much knowledge as possible. In my "Fairmont days", I repaired cars by buying parts til it ran again.

Havn't got the dough for that anymore! Just need to understand the theory of it all so it isn't as much of a mystery. I've seen engine build ups that used different cams to "lower comp. ratio", or more correctly "bleed off cylinder pressure". The car doesn't come stock with "blower cams". Are there "blower cams" available? Wouldn't blower specific cams really help a s/c mm?

I just sence a crutch here somewhere with s/c mm kits thats holding them back. Thanks again for the great thread!
 
Leadfoot281 said:
Are there "blower cams" available? Wouldn't blower specific cams really help a s/c mm?
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Not really. At least there aren't any cams that will produce enough gain to make it a worth while venture. The heads and cams on the 4.6 DOHC desgin are VERY efficient right from the factory. And they provide excellent driveability. Its a formula most builders would advise you do not tinker with. Some of the high end racers do change cams, but they are not concerned about street duty, nor do they car about the cost/benefit factor as much (as they are looking for every last tenth).
 
Leadfoot, once again, I believe that Mike is steering you right, and I again agree with what he's stated. And in addition to what Mike has said, I want to add that you need to keep in mind that all the testing, research & development that has gone into atleast one or two of the supercharger kits available specifically for the Marauder has been performed with the stock camshafts. I know for a fact that's the case with the Trilogy kit.

So for using different cams, it's going to take some extra engine tuning to get everything right, and to safeguard against engine pinging.
 
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BillyGman said:
So for using different cams, it's going to take some extra engine tuning to get everything right, and to safeguard against engine pinging.
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It's also going to take some extra $$$$!
DOHC Cams (all 4 of them) cost @ 1,200.00 for a set!! :eek:

I got 'lucky' and bought a set of Crower 'Baja Beast' DOHC cams for $980.00.
The 'Baja Beast' cams run more lift, but not a lot of extra duration. They are meant for heavy vehicles and should not kill the DOHC's limited low end torque.
 
Hi All,

I am a new member & not that computer savey. My first time chiming in, I just installed my own Trilogy Super Charger standart kit w/PCM chip by Lidio. Installation was very easy, the directions were great! The best fuel I can get her is AZ is 91 octane & the kit performs perfectly!! I couldn't wipe the smile off my face for two days!!! The kit is designed for a stock MM & the car behaves the same as stock until WOT. I'm very happy. I had a lot of the same apprehensions about it on a 12,000 mile "04. It was 113 degrees yesterday & I beat on the car for a half an hour & absolutely no detination, no overheating, so that pretty much passed my test. I made a phone call to Lidio to say Thank You and let him know the transmission mods I had done previously worked well with his tune. This is the car Mercury should have made!

Trilogy #92
 
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