Trumpet height

Bill Bayard · 04-23-04, 07:11 AM

I thought that this might be of interest for those trying to squeeze the tallest possible air horns under their rear window.

Bill

Ron Earp · 04-23-04, 07:51 AM

Interesting - what motor is this being dynoed, diameter of horns, etc.

JP · 04-23-04, 08:25 AM

That is most pleasing, I'll be keeping my short trumpets then. [img]/ubbthreads/images/graemlins/grin.gif[/img]

I did wonder what effect it might make by increasing them by an inch. And who ever said bigger is better!

Regards,

J.P

Frank Catt · 04-23-04, 08:26 AM

Ron, if you are still intent on useing IDFs, I found some mods that worked on the air horns (trumpets) that improved stand off, Frank

Peter D · 04-23-04, 09:36 AM

Bill, I am going to stick my neck out on the chopping block here !

My (probably naive) understanding is that as a general rule & all other things being equal (there's a dumb phrase I remember from Economics!), short trumpets = higher hp, less low-down torque & long trumpets = lower hp, more low-down torque.

The big plenum & long intakes on 90's Vette engines are probably responsible for more whiplash injuries off the lights than rear-enders !

However, with bucket loads of both hp & torque on most tweaked 8-stack setups, the differences would be hard to pick on the road. A 5hp diff could easily be wiped out by turning on the A/C & rad fan !

For road drivers like me, it probably comes down to aesthetics, what came with the kit, and what will fit !

Kind Regards,

Peter D.

Adam C. · 04-23-04, 09:58 AM

I'm still trying to figure out 225 hp at 8,000 RPM. [img]/ubbthreads/images/graemlins/confused.gif[/img]

Gary Gibbs · 04-23-04, 10:16 AM

Must be a lawn mower engine with only 147 ft-lbs of torque at 8000 RPM.

JP · 04-23-04, 11:45 AM

Nah, sounds more like the power used to drive my wife's hair dryer! [img]/ubbthreads/images/graemlins/grin.gif[/img]

JimmyMac · 04-23-04, 12:53 PM

Gents,
The graph is interesting, but the minor deviation shown above 6000rpm does not phase me personally as I will not be pushing my own block above 6k for long, even though I have a solid four bolt mains.
Why mess around with the low impact changes to air horn volumetric flow when we should really pay more attention to getting maximum efficiency from a good head set up and eliminating power loss through front end belt driven systems ?.
The original Weber horns did well enough at Le Mans so I'm afraid for me it's "get back to basics", unless you think that an inch or two on air horn length really counts.
Are we possibly talking about another one of those High Street status symbols ?. If so, please count me in !.

Howard Jones · 04-23-04, 01:54 PM

Adam, I'm sure you noted the "SAE Corrected" note. Might this have something to do with it? The other thing is how flat the HP curve is above 6K. Could this data have come from computer modeling software? Hummmm.... at any rate the shorter air horns look better IMHO. And thats what they are good for on a street driven car anyway... looks.

BenL · 04-23-04, 02:34 PM

What are the heights of the "short" and "tall" air horns?

Ron Earp · 04-23-04, 02:52 PM

I would guess this is a 2.0L naturally aspriated 4 cylinder - anyone gonna tell us?

Kevin M · 04-23-04, 03:21 PM

I'd go with Ron's guess. Do they make stack FI set-ups for Hondas?

Kevin

JP · 04-23-04, 03:26 PM

[ QUOTE ]
I would guess this is a 2.0L naturally aspriated 4 cylinder - anyone gonna tell us?

[/ QUOTE ]

Ron,

Like I said its a Remmington of some kind!

J.P [img]/ubbthreads/images/graemlins/grin.gif[/img]

Howard Jones · 04-23-04, 04:59 PM

ah... that should have been flat above 7000RPMS. This goes to show you how narrow my focus is on all things GT40. I never considered it wasn't a SBF. At about 1.5hp per inch it looks something like 2.2 liter. Thats quite a lot of power for that small a NA motor. Maybe a dohv V6 or it could be a old ford cosworth alantic motor, I think they made about this much power, or some other 4 banger race motor.

Stack height would be dependant on what the motor was being tuned for, track, rev range, needed torque curve, power curve, engine size and layout, number of valves, cam layout etc, etc,. Real short would be 2 inchs and real long would on the order of 10 inchs. Pictures of drag race normally aperated V8s look like about 8 inchs, I have a really good picture of a f alantic car with webers on a 4 banger ford with stacks that look like about 3 inches and the orginal GT40 SBFs look like about 2 inches. Go figure.

Adam C. · 04-23-04, 07:01 PM

Not that I want to pump my own material, but has everyone seen this earlier thread?

http://www.gt40s.com/ubbthreads/show...b=7&o=&fpart=1

We've been there, done that. [img]/ubbthreads/images/graemlins/cool.gif[/img]

Bill Bayard · 05-03-04, 09:35 AM

The dyno sheet above is from a 1750cc Alfa engine.

It has tin 40mm Weber DCOEs, as well as a few other tweaks.

Not bad horsepower from a little four banger!

Bill