No, the Briggs and Stratton could NOT theoretically make the same power. You can only pass so much air through a 3/4" hole, no matter how hard you push (boost). No "theoretical" about it.

And no, the "other airpump" (the engine) can NOT "only move as much air as it is fed by the blower." What you're missing is that the engine can only move as much air as it is fed by the blower, UNLESS the intake or exhaust ports are a restriction.

Think about that one for a second.


So therefore a supercharged engine with a potato in the tailpipe will lose very little power? Nope. I dare anyone with a Lightning to restrict their exhaust and lose a "very small" amount of power.

I'm more than familiar with the various xMEP's (Mean Effective Pressure). I've looked at cylinder pressure data before - including on supercharged engines. Something else you're missing is that the expansion part of the curve being greater relative to the exhaust portion has nothing to do with any alleged lack of criticality of the exhaust portion. It has to do with how modern street engines are cammed.

You're a bit confused about a couple of issues. You say that "On a naturally aspirated engine, pumping loss is very important." What you need to understand is that the supercharger covers up quite a bit of the inlet side losses that a naturally aspirated engine would suffer. However: Contrary to what you say, a supercharged engine is MORE sensitive to pumping losses on the exhaust side, more so than a naturally aspirated engine. This is because the naturally aspirated engine has less residual mass (internal EGR) in the cylinder to begin with. At WOT, cylinder pressures are, in most cases, lucky to approach ambient pressure. The reason you and everyone else think not is that 1) the current crop of headers on the market are not optimized and therefore don't demonstrate the full power potential of a Lightning, and 2) a supercharged V8 makes so much power (in relative terms) that it's difficult to gauge small percentage changes in power by the seat of the pants.


No. Plug your L's tailpipes most of the way, and you'll see the opposite to be true. The key point you've missed is that the supercharger is delivering the same VOLUME of air, NOT the same mass.

It's not just a question of pumping loss, it's a question of flow. Plug up your tailpipes most of the way, and boost will go up, and flow will go down.

No! Again, if that were true, simply putting an M112 on a tiny 4-cylinder engine (or smaller) would produce 380 hp. The real story is this:

An engine with an M112 could potentially make around 380 hp ONLY if it had the ability to ingest that much air. Period. Argue all you want, that's a fact.

If you think otherwise, then I have an zero-power-loss intake gasket to sell you - It has ports that are only 1/4" diameter, but your Lightning will still make 380 hp because the engine has a 112 on it, right?

You have, but you went over it incorrectly

Completely wrong. Downstream mods make a BIGGER difference than on a naturally aspirated engine, IF they are designed correctly.


You're grasping at straws. "Lower pressure of the blower inlet"?! The Cobra intake tract isn't that bad, and doesn't create a vacuum at the inlet as you say.

Inlet density will go down almost as fast?! You're saying a pulley upgrade on a Mustang will create a vacuum and airflow will hardly increase. Let's make a third bet! Any other experienced racers want any side action on this?

There are more than the two differences you say between the L and Cobra. The Cobra is a different displacement, has what amounts to a totally different cylinder head, and revs to a very different peak rpm.

You're on the right track, but many, many people have already gone down this road. It's not called dual stage compression, it's called compound supercharging. The problem once again comes down to the massive amount of crankshaft horsepower the two superchargers will consume. Get your input horsepower numbers from the centrifugal companies. You'll see.

School's out.

 

truckn = bonehead

I won't waste my time on her/his response.

 

Its obvious we have differing opionions on this so I'll keep it short.

The mass of air through the constant volume device is a function of swept volume, inlet density, and rotational speed. If you force it through the smaller hole, or more restrictive engine, the outlet pressure (boost) will go up, raising the power consumed and heat generated by the blower. Will your measured HP be less? Sure. Will it be significant (if this is the same engine we are talking about)? No. Not on an egnine with a 380 HP rating.

Go find some blower data and show me that at larger dP's, the airflow goes down. If you loot at eatons's own specs, the lines of airflow at different DP's are nearly on top of each other. What's not on top of each other are the power and temperature curves.

Will 1/4" intake gaskets hurt power? Yes. Why? Bacuase the power consumed by the blower will go up. Will airflow go down? No.

Taking the argument and applying it to a B&S is stretching the generalizations a long way. What was the intent of the post? Modifying the lightning engine and how airflow changes. There are way too many changes involved in applying the same principles to a B&S.

By the way, I never said the Cobra's intake was restrictive. I was talking about the SVO blower kit for the GT's.

Since I'm sure you still disagree, we can continue the discussion by email.

 

Perhaps a little background is in order for truckn and other people that are wondering where some of these comments are coming from.

The Eaton M112 was used as the supercharger option on the SVO kit for 96-98 Mustang GT's a long time ago. The majority of the experience, at least in the Mustang community, is centered around centrifugal superchargers by Vortech, Powerdyne, et al. The modification strategies that people commonly applied at this time were the result of experiences gained from using those types of superchargers. Very little firsthand experience with roots-style superchargers existed within the Modular Mustang community (the Kenne Bell supercharger was not yet available for the Modular engine). I myself did quite a bit of work on several cars with the SVO kit back then.

The initial stages of midification past the base supercharger installation went well. A smaller pulley here, a revised MAF and transfer function there, and some gains were made. It was well known at the time that the stock 96-98 GT heads were horribly restrictive, and the Vortech guys had made some impressive gains when they swapped to a set of ported SVO heads. The Eaton-supercharged guys closely followed suit.

Typical gains? 60-80 rwhp for most of the Vortech guys, as low as 15 rwhp for the guys with the SVO kit.

Why?

Because your modification strategy has to be based around the nature of your engine's induction. There is a huge fundamental difference between a roots-style compressor (by nature a constant volume device) and a centrifugal supercharger (which has a volumetric flow closely related to the pressure differential across the blower). When the Vortech guys swapped on ported heads, the volumetric flow through the blower went up with the reduced pressure differential. The SVO guys had a blower whose volumetric flow was determined only by rotational speed and inlet pressure. The downstream pressure (or differential pressure) was involved only to the extent that it determined the amount of horsepower necessary to turn the blower itself- a small number compared to the power gains made by other means.

So why weren't they able to get the additional flow needed by spinning the blower closer to its 12,000 rpm maximum? Two reasons.

Actually, he's correct. You just misunderstood what vehicle he was talking about. We did some work back then and discovered that there was a significant inlet restriction in the way the Eaton M112 was plumbed into the 96-98 GT kit. This, along with the reduced efficiency of the blower at higher rotational speeds, was effectively limiting the amount of power that could be made with this kit in a streetable form.

Luckily for this group, it appears that the L has no such inlet restriction in the M112 plumbing, so it should be relatively easy to keep the blower inlet pressure at a reasonable number even at higher volumetric flowrates. This doesn't negate the nature of the blower in helping to determine your modification strategy, however.

I don't think anecdotal reasoning involving a 380 hp Briggs and Stratton is going to prove your point. What I believe Mr. White Lite was suggesting is that assuming the head design and port size is reasonable for your volumetric flow (ie, you're not needlessly backpressuring the blower and getting some outrageous discharge temperatures/hp consumption) then further bottleneck reductions at the head via larger ports or other head modifications is likely a waste of your time. The Eaton simply will not take advantage of the reduced downstream pressure in the same way a centrifugal supercharger will. If the head modifications are done at the same time as a blower change or dramatic increase in volumetric flow (where the above mentioned discharge temps and blower parasitics may come into play), then it is far more likely to be a worthwhile endeavor.

I'm not going to comment on the exhaust aspect of things since I don't have nearly the volume of experience relating to how exhaust mods correlate with the type of forced induction. To me, it seems less relevant since it is effectively isolated, internal EGR aside, from the compression source itself.

Again, I think the extreme reasoning regarding B&S motors and completely plugged up exhausts is not likely to prove anything regarding how small changes will affect overall power output. Almost all the engine modification options are reasonably balanced in comparison to the extremes, yet many of them still don't offer worthwhile power compensation for the time and money spent on them. Choose wisely.

 

I'm not a mechanical engineer and have little input, but I do have a question. If we put smaller valves in our motors would the power remain the same? If so, that would conclude that head work doesn't change power.

I had larger intake and exhaust valves installed and a little head cleaning. It seemed to make a difference, although I haven't run the truck to back it up. Even a 25hp increase would only result in a tenth in the 1/4mile, at most.

 

You're also missing the point?

Reread the entire thread.

This is a package deal. It was engineered correctly from the factory, more or less.

Yes smaller valves would probably decrease the flow of a/f to the head. but in it's current form it is efficent.

Try looking at it this way. You have a bucket of water and a hole in the ground which is big enough to poor the water into as fast as gravety will permit (does 8 psi sound familiar?). Now you want to poor the SAME amount of water in the hole faster, so you make the hole larger???????????????????????????????????????????? ??????????????????????

This isn't the correct modification to make is it?

You need to force more air and fuel into the head, and not reliy on the effectiness of the aerodynamics of intake charge. Hell it's being forced into the head who cares about the heads ect....

Another way to look at this is yes my heads suck, so do I fix the heads or in our case just gets a bigger blower? Also with the bigger blower come a minus with head, headers, ect... are you starting to see the "package deal"?

BTW our heads don't suck at least for most +20% club racers out there!

 

Uh... I notice that when the pedal is closer to the floor, it feels like I am making more power. When I let the pedal come off the floor, it feels like the power goes away. And when I floor the pedal, but hold down the brake at the same time, the power sounds like it's still there but I can't feel it anymore. I can only SMELL it... or something.

BTW, for anyone who's interested, here are some pics of that crazy Honda NR500 engine (what a beast!):

 

Ya, I'm the one who started the NR-500 mess.

If you think that's a ball buster, back in ~1985 Honda came out with a F1 engine that was about 100ci that made 2200hp! < that's not a typo.

FIM baned it after 1 qualifing session. Again oval pistons ect...........

Thanks for the pics.

 

Wow, that F1 engine takes the cake! What I really want to know is... what happens if I put a few potatos in this car's exhaust?

 

ROFLMAO, stop it you're killing me!

OK another one,

Honda made a street going nr-500 called the nr-750 ( they also raced one in France also called nr-750 earier that year Bor-d-org? hell cup of gold). I heard that they go for over $1,000,000 today? I think that they only made 200-400 of them.

Oh btw oval pistons, ect...................

 

99 White Lite- Since you know about both the L and The 03 Cobra, I was thinking of selling my L and buying a cobra. What would you suggest for mods on the Cobra, (the most power for the money, eff., etc...) And if you have time what would you suggest for the L. It would be greatly appreciated.

 

Not to go against you, but my @ss-o-meter test says the truck felt like it made more power after the complete exhaust (LT, cats and muffler). And to further back it up, I can now break the tires loose when going WOT @ 35mph, something it didn't do before the exhaust. Neither of these are empirical (sp?) data like Beefcakes before/after dyno which only netted him some HP across the dyno plot. I'm not saying the whole exhaust will create great power, but I say it does more then "a 1000 dollar full exhaust won't do anything"

No don't do that. Trust me alot of people are enjoying this discussion. I know I am.

 

*munching popcorn*

YES, please resume the discussion HERE! Don't make us wait for the DVD to come out!

And now, back to your regularly scheduled Honda commercials...

 

My guess would be the same thing as a cork placed up a fat dudes butt that ate to much beans.

Whoever is standing behind needs to move

 

Them there fight'n words!