P6 air filter dyno test

quattro said:
Would there be much difference if you ran the engine in a hot engine bay, rather than out of the car hence running on cooler air?
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Air temp does make a difference to power, but its not massive, in any case testing conditions were the same for all sets of tests they were all done on the same day, same coolant and oil temps. oil temp in particular makes a bigger difference to power than most would expect.
 
I recognize there are many other induction options that you could consider for this comparison.

Perhaps one which may be quick is the removal of the air can, internal filters and elbows and fitting of the filters directly to the carbs.

This might confirm if the torque output is sensitive to the presence of the elbows and filter can or not.
 
eggbert68b said:
I recognize there are many other induction options that you could consider for this comparison.

Perhaps one which may be quick is the removal of the air can, internal filters and elbows and fitting of the filters directly to the carbs.

This might confirm if the torque output is sensitive to the presence of the elbows and filter can or not.
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they don't look right
 
Hi, I can remember reading an article many years ago about having the air filter as close as possible to the carb intake. It stated that with a long gap at full throttle the column of air has a lot of inertia and when the throttle is snapped shut it has to go some where, maybe into the float chamber and empty it or any other way out, all in all unsettled running until it recovers. The filter acts as a damper. I can't remember all the finer details of the problems but when modifying cars over the years I've heeded the issue. It does make for neater installations and was what the manufacturers did at the time but not so much nowadays with the use of plenum chambers and concertina intake hoses to absorb it.

Colin
 
GRTV8 said:
they don't look right
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I agree - but looks aside, I presume there is a reason for the elbows and filter can set-up given it would cost less not to manufacture and use them. Other than Rover V8s, I don't know of another V8 using a similar elbow / filter can arrangement. Bentleys / Rolls have similar but with the filter placed local to the intake snorkel at the front of the car.

If they do have an effect on torque, does than imply Holleys / Webers lose out on this effect having the filter mounted on top.
 
I can't find my copy to check but Des Hammill's book reckoned the best set-up was elbows and free-flowing filters in a standard airbox with a plate between the filters - I don't remember which airbox it was but if my memory serves I think there was something like 15hp difference between this and filters straight on the carbs.
 
ratwing said:
I can't find my copy to check but Des Hammill's book reckoned the best set-up was elbows and free-flowing filters in a standard airbox with a plate between the filters - I don't remember which airbox it was but if my memory serves I think there was something like 15hp difference between this and filters straight on the carbs.
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i have a few of Des hammills books, dont argree with everything he says, but from what ive seen that 15bhp could be feasible
 
Can you provide more insight as to how the elbows improve engine torque and/or bhp. I note Colin's comments above the inertia of a column of air along the elbows could be a factor.
Why is that Holleys/Webers generate improved induction given absence of the elbows.
More for my own understanding - thanks
 
Eggbert,
An engine is not measured only by its peak BHP - its torque curve shape is very important. with an auto a poor (read mostly peaky) curve can be disguised by the torqe converter, but with a manual box you will be changing gear a lot more. After my first back-to-back drives of 10.5:1 and 9.25:1 manual box cars I resolved to look for 9.25:1 cars as they were more flexible, with more low down torque than the 10.5:1 engine. When you speak of other carbs producing 'improved induction' are you implying that means better torque spread, or are you comparing apples and oranges? They seem to be well known for more BHP, but I havent actually seen a torque curve for a Holley or Weber. Else where here there was a post about the factory trying Webers on a 4 cyl engine, and the small gains were'nt worth the down side.
 
Hi, Holleys and Webers feel different because they have an accelerator pump, when you prod the throttle they squirt a jet of fuel down the throat to aid acceleration and so feel more responsive compared to the SU.

Colin
 
eggbert68b said:
Can you provide more insight as to how the elbows improve engine torque and/or bhp. I note Colin's comments above the inertia of a column of air along the elbows could be a factor.
Why is that Holleys/Webers generate improved induction given absence of the elbows.
More for my own understanding - thanks
Click to expand...
Webers and Holley make more power because the carbs themselves flow more air, but also they are fitted to more efficient intake manifolds.

elbows help torque because they make the inlet tracts longer, long intakes tend to pick up low speed torque, what you have to realise is the air in an intake manifold isn’t all smoothly flowing in one direction, the manifold has a jumble of pulses going in and out, they greater intake volume with the elbows added to the interia the incoming mixture has so more force f it ends up rammed into the cylinders
 
Would polishing the internal part of the elbows improve induction? As a teenager back in the mid 60's we were obsessed with any port and polished head. I had my Mk1 cortina done because it was fashionable. Didn't get the bang for buck on the head.
 
GRTV8 said:
Would polishing the internal part of the elbows improve induction? As a teenager back in the mid 60's we were obsessed with any port and polished head. I had my Mk1 cortina done because it was fashionable. Didn't get the bang for buck on the head.
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i cant see polishing the inside of the elbows would do anything except take up your time!
 
if I recall correctly polishing to mirror like finish on intake gives no improvement and a more golf ball like ( casting) gives better flow rates .( hence why golf balls are pitted /crater surfaced) its the exhaust that needs gas flowing for better gas speeds and ideally exhaust pulses are sorted eg 4 into 2 into one pipes so cylinder scavenging is good.
 
Thanks guys for the education here.
By induction I was generally referring to the relationship between torque distribution over the rev range and peak generated power. I recognise there is a compromise between the two.
I recall the quote from Shelby, ‘horsepower sells cars, torque wins races’ or along those lines.
much appreciated
 
In civil engineering, within the context of fluid flow, surfaces are given a Mannings 'n' value, which is a measure of roughness. Smooth surfaces allow improved flow when compared to rough surfaces. It all has to do with boundary layers and the effect on flow, either laminar or turbulent.
In the case of an air intake elbow, a rough surface generates turbulent flow, and for a gold ball, this assists it to travel further.

Ron.
 
One way to know if the inside surface roughness of the elbows makes a difference would be to conduct an experiment. With all else remaining exactly the same and all parameters recorded, test the output with two pairs, one smooth, and one rough, and compare the results.
Alternatively, this article will provide guidance on turbulent flow over rough surfaces. The pdf can be downloaded free of charge.
A review on turbulent flow over rough surfaces: Fundamentals and theories - ScienceDirect

Ron.
 
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