99'white lite

Ummm, I made the comment about tuning the B&S and I am sorry for that. I kinda got caught up in this thing and some other posters took some pot shots at truckn and so I took one back.

I was just being a smart a$$ and didn't mean it, this is a good thread and I wanted to see it keep going, you guys have a difference of opinion and in the mean time I'm learning something.

I do have one question.

A local guy in the lightning group around here made some changes to his gen 1 lightning over the winter. His truck has a stock 351 with a powerdyne super charger on it. Before the mods he had 8lbs of boost and made right at 325 hp....truck ran 13.50's. He has since changed cylinder heads to the GT-40X heads and a set of 1.7 ratio rocker arms, the heads were ported by good shop on the exhaust side only with some nice gains.

The truck now makes only 6lbs of boost, hp has gone up into the 385 range and it now runs in the 12.70's (this was also with some razor sharp tuning on the computer chip).

My question is this? If Steve had a roots style charger on his truck instead of the centrifugal are guys saying that this could not or would not have happened.
Thanks Dale

 

So you are saying that if we saw a 2# reduction in indicated boost happen, it was a case for the x files since it couldnt have or shouldnt have.... The guage was wrong or we read it wrong or we were mistaken....

I knew if I had finished college I would understand what I see with my own eyes better ....


Doug

( or to translate my sarcasm - The real world is not always according to the books... )

 

I am a little bit confused Is this an actual event you saw, or are you just being sarcastic (as you say later)? If its sarcastic, then yes, you're going to have to call Scully and Mulder. Unless it happened after Mulder went away, then Scully will have to handle it on her own By the way I'm not a super geek and don't watch x-files, just in case you were wondering

That is exactly what we are saying. In fact, that is the whole "argument". So many people have dealt with the centrifugal blowers that the data from those engines are all over the place. Roots style blowers, on the other hand, have long since been abandoned (for the most part) by the aftermarket. Mostly because of these issues. Centrifugal blowers, in general, are much easier to make more power. Then the same people go and try to apply the same principles to another type of blower, and that just doesn't work.

OEM's continue to use the roots style blower because of the reliability, and probably the added low end torque.

 

Hey since this is a wonderfull discussion going on here is something else to chat about.

I was reading on another board a discussion about power to weight ratios, torque being not that important (an import car message board) and one of the guys had this to say:
Something about this just urks me, can't put a finger on it. But since everyone is discussing technical stuff about how engines and blowers work why don't we through in some more fun stuff

 

This probably deserves its own thread, but here's my take on the situation.

The only thing that matters is power and weight. Weight is obvious. F=ma, so a = F/m. If "m" is bigger, "a" is smaller. Power is also obvious, but the reason might be cloudy. Peak power (the number most quoted) is useless. The real measure is average power across the usable rev range. For a L, the lower end of the spectrum is the rpm you fall to when the truck shifts to second. The high end is the shift points.

For outright acceleration, it doesn't matter if you make 400 hp at 6000 rpm with a torque peak somwhere of 400 lb-ft, or if you make 400 hp at 12000 rpm witha tourqe peak somewhere at 200 lb-ft. What matters is the average HP across the rev range. Typcially, the rice rockets (a civic is a rocket????) don't make the same kind of average HP accross the rev range.

Try and think about it this way. The maximum acceleration in any gear is at the torque peak. Once you past the torque peak, you are not accelerating as fast. The maximum acceleration at any speed will occur when the gearing is chosen so that you are at maximum HP. If you put a supercharged and turbocharged civic engine with NAAAAAAAAWWWWWSSSS that made 400 HP at 9000 rpm, and then put in some 4.56 gears (or thereabouts), it should accelerate similarly at peak HP. But if the average HP on the civic is lower, the average acceleration will be lower.

Now lets talk about real world. Since you're driving around with you L close to the torque peak, you can romp on it and accelerate right away. The civic engine would have to be downshifted and you have to rev the snot out of it to make it go. Typically the civic engine would be operated farther away from its torque peak in day to day commuter driving. Also, relibility from any heavily modified hi-revving engine will be compromised.

So that was the long way of explaining that peak torque isn't that big a deal for out and out performance, but it sure makes it a hell of a lot more fun to drive around. There is no replacement for displacement!!!

 

. . . is that downstream mods may pay dividends when the engine is not on boost, which is 99% of the time for most people. The supercharger is irrelevant under vacuum conditions, right?

If the acceleration is more brisk even off boost after a downstream mod, it may produce a subjectively more satisfying experience, even if a dyno pull will not demonstrate it.

Still gonna be the last place I look for power, but an ever-so-slightly more aggressive exhaust note wouldn't hurt my feelings.

 

"Rev the snot out of it" LOL......you SWRI guys wouldn't happen to know a fella named Todd King do you ?
Dale

 

Nahhhh, this is one of the best information threads I've seen on here. Why not just overwhelm it with usefull information. Then one day we can archive it somewhere for all interested to read

Actually he was to refering to bikes, not cars. And civics are not rockets.

 

I was kidding! I know he was talking about bikes. I offered up the civic as a rice rocket comments, since I have heard people refer to rice cars as rice rockets. Bikes were crotch rockets.

And you are right, civics are NOT rockets!!

 

AMEN AMEN !!! Detroit RULZ ....

And this is one of the best threads here!!!

 

somebody let me know if im wrong, but didn't the 03 cobra pic up like 30rwhp or more with a free flowing exhaust?
i dont understand how opening up the intake ports and exhaust ports wont help get more air into the combustion chamber. Even if the blower only flows a certain amount of air per revolution of the rotor why should that be a issue? its not like the engine is using all the air that the blower is moving anyway, if that was the case then the boost gauge would read 0, the motor makes boost b/c of restriction right? so if you let more air in, and more air out your removing the restriction and getting more air into the motor. if you lose 1-2 lbs of boost from a set of longtubes that just shows how well they are working, and if you port your heads and lose a pound or two, the same. hey thats just what i think, im not a engineer, still going to school. but it sounds logical, but feel free to tell me if im full of #$&*.

 

OMG - someone resurrected the "Thread of Dread!"

I hope we learn as much from this go-around as last time!

 

lol........whoops....had nothing better to do.

 

That's ok... I think this thread will take over as the new "Thread of Dread" in a few hours!

 

So here's a stupid question...since headers, ported heads and cams don't show much power gain with our roots blower, will they show big gains with the new screw blowers (KB, 140)?