On a centrifical supercharger that claims a 30% gain in horsepower, would that apply across the board? {i.e. a 300 hp to 390 hp, 400 hp to 520 hp, etc}

I say no, because the supercharger overcomes flow inefficienties with lower powered engines, so the gain is lessened with more efficient engines. What do you guys think? Has anybody seen dyno comparisons at different level base horsepower engines?

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
MCA Member # 47773

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
MCA Member # 47773

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
MCA Member # 47773

Here is a link to some of Chris Johnson' comments on the truck:

http://www.jmschip.com/oldnews.html

He is probably one of the best chip burners in the business.

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James
67 Coupe
393W, AFR 185, 4 Speed, 4.11 9 inch
7.09 @ 97MPH 1/8
1.55 60'

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

Not if you're keeping the drive speed constant. However, to a first
approximation, you might expect the total horsepower increase to be the
same (300 to 390 HP, 400 to 490, 500 to 590, etc.).

The gain a supercharger provides is dependent upon its flow rate, as limited
by the compression ratio of the engine. A supercharger is basically a pump,
with a given flow rate versus impellor RPM curve. If one engine inhales
twice the flow of another (for instance, a 250 HP 5.0 versus a 500 HP 460),
it will require twice the flow out of the supercharger to provide the same
boost (all other things equal, to a first approximation). This disparity
in supercharger flow rate versus engine boost level is why boost is not a
good measure of a supercharger. A lower boost level can mean either the
engine is efficiently passing it's flow through the engine or it can mean
it's uselessly blowing the boost out the tailpipe (due to excessive cam
overlap). A higher boost level can either mean the supercharger is producing
a lot of flow or the engine is restricting the superchargers output. Boost
can be useful but you must know the context.

There are various types of superchargers, some are positive displacement
(Roots and Lysholm intermeshing screw) and some are not (axial and
centrifugal flow). Both types of blowers produce flow as a function of
impellor speed. The primary difference is how the boost varies with RPM.
A positive displacement supercharger sweeps out a fixed amount of flow
with each revolution of the impellor so flow varies linearly with impellor
RPM. Double the speed and you get double the flow. Axial (Latham) and
centrifugal (turbos, Vortech, Paxton, etc.) superchargers produce flow
that is proportional to the square of the impellor speed. Double the
sped and you'll quadrouple the flow. That may seem like a good thing
(more flow = more boost) but it's not. The nonlinear flow curve limits
the working range of a centrifugal supercharger. Pulley one to produce
meaningful boost at 2000 RPM and you'll over-boost the engine at 6000 RPM.
The linear output of positive displacement blowers allows them to operate
over a wider RPM range without overboosting. Turbos get around this by
installing wastegates which bleed off boost above a certain level.

A direct by-product of supercharging is an increase in the (dynamic)
compression ratio, with an attendant increase in temperature (pressure
times volume is proportional to temperature for an "ideal" gas... PV=nRT).
This is why it's a good idea to reduce the static compression ratio when
adding a supercharger.

quote:

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Originally posted by Moneymaker:
Let's see now, the article says a previous best of 13.18 and you say 14.00. Which one is it? That's about a second disparity there.

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That was with the blower installed as delivered from Vortech 6-rib pulley, stock 19lb injectors. Dropped from 14 flat to 13.18. Took it down to him installed the injecters and then tuned it in with the proper A/F ratio and it dropped ET to the 12.20's in 90 degree heat. Ran 3 11.90 passed later that fall in some 50 degree temps. It was pig rich(safe) the way Vortech has them tuned. There's no way a early Lightning with the limited mods I had and still speed density would run low 13's. Don't worry your not the first person to doubt how well that truck ran for the limited amount of mods I had on it. It had them where it counted. Heavly ported exhaust ports, cleaned up intake and lower intake ports also a full off-road Bassini exhaust and 12 psi of boost will do wonders. At the track with race gas and the boost timing retard turned off it picked up about 50hp over the street tune.

All I was trying to say was I went from somewhere over 300hp to over 500hp just from the addition of a supercharger which is a little more than 15%. 95 mph naturally aspirated to 112 to 114 mph supercharged at 4200lbs, plently of on line calculators to figure the HP. Anyway no big deal I joined this site to learn how to make a early model Fords with leaf springs haul butt and I came to the right place.
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James
67 Coupe
393W, AFR 185, 4 Speed, 4.11 9 inch
7.09 @ 97MPH 1/8
1.55 60'

[This message has been edited by 67Coupster (edited 03-29-2002).]

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

quote:

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Originally posted by Moneymaker:
His name is Jim Gilbert from Ohio and if you know anything about Lightning racing you know of Jim.
All you have to do is manage to keep the head gaskets and pistons in it.

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Jim's truck is awesome. I had the pleasure of seeing it run at a couple of the FFW's when I was running in the stock Lightning class.(When it was still heads up racing) Your dead on about the head gaskets I blew one right before I sold the truck. Talk to ya later!!

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James
67 Coupe
393W, AFR 185, 4 Speed, 4.11 9 inch
7.09 @ 97MPH 1/8
1.55 60'

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Neal
Member #723
[email protected] AIM: MrWesson22

Thanks guys! Pretty basic stuff when it comes to supercharging. I had a leg
up on understanding supercharger theory from my jet engine and turbomachinery
classes. Jet engines and superchargers have a lot in common. The axial flow
Latham supercharger is basically just the compressor stage of an axial flow
jet engine. Likewise, a centrifugal supercharger is much like a centrifugal
jet engine.

>I will say that James's Lightning was one of the fastest speed density trucks
>in the Lightning world.

I didn't realize it was speed density. What was done for tuning and the
fuel system? I recently purchased a Novi 1000 kit and intend to install
it on my daily-driver '87 Mustang GT which still has speed density.

>Speaking of supercharged Lightnings......

Have you guys heard any reports on the 5.4L supercharged Lightnings? A friend
has one (recently dyno'd at 365 RWHP on a dynojet). He mentioned that there
were something like 48 engine failures on the Lightning email list he's on.
To be fair, these are guys who are turning up the boost but with the very long
stroke of the 5.4L, it looks like connecting rods are a weak link.

quote:

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Originally posted by Daniel Jones:
>
I didn't realize it was speed density. What was done for tuning and the
fuel system? I recently purchased a Novi 1000 kit and intend to install
it on my daily-driver '87 Mustang GT which still has speed density.

Dan Jones

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Fuel system was the Vortech T-rex inline fuel pump along with 30lb injectors. Needed at least 36lb injectors on my combination as it was leaning out above 5000 rpm due to the injectors going static. I'm sure that's why I popped that head gasket right before I sold it. As I'm sure you know the speed density system has a few limitations. Works pretty good at WOT but I had a few driviblity issues that I never did get worked out. All the tuning was done by Chris Johnson(Chris Johnson Motorsports) down in Mobile, AL using Mike Wesleys chipmaster software. I would highly recommend going to mass air and have it tuned with a wide band O2 sensor. The kits come way rich and you can pick up a ton of power while still being safe with the proper tune. Later!!

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James
67 Coupe
393W, AFR 185, 4 Speed, 4.11 9 inch
7.09 @ 97MPH 1/8
1.55 60'