Power gain with smooth intake pipe???

[JMF894]

I have been reading some RV8 tuning websites this afternoon and some suggest that replacing the standard plenum elbow with a smooth bore pipe such as silicone or polished metal may give a modest gain in power. Whilst this makes perfect sense in principal due to the better, smoother flow of air, has anyone actually any real evidence or experience of this?

Jimbo

[mrzigazaga]

Metal air pipe will soak up heat and give you no power gain..More and likely make it worst..Cold air induction would make a difference although not massive 3-5 BHP..Making the air inlets bigger obviously would give you more power but more air requires more fuel..Even on my 280 there is an air trumpet next to the distributor that has a big curve in it because of the dizzy..Burton power used to fill them and rebore it which could give an extra 15BHP which is a lot for a small mod..You could always lag your manifolds and fit heat sheilds..I think you need Profiled cam..Big bore valves..Gas flowed and port polishing..Up-rated fuel pressure reg..And then one of these to give you cold dense air..Go on you know you want to..
http://focus.c-f-m.com/browseproducts/S-MAX-Ice-Tu...
http://www.v8tuner.co.uk/product.php?id=679
http://www.v8tuner.co.uk/product.php?id=601

You would need to phone to check fitment..Ziga

Edited by mrzigazaga on Wednesday 20th July 20:56

[wedgeinald]

Zig.....Why not just buy a used one of these?



2010 Cosworth F1 Engines for those who don't recognise them...

[mrzigazaga]

YUMMY..Ill have two slices...

[Wedg1e]

B-Reight said:

Cut the trumpets down by 18mm, what a revelation! It now revs cleanly all the way to lifter pump up at 5800rpm, previously it stopped dead at 5k and made peak power of 218 @ 4950 rpm.

So it looks like the trumpets were the bottleneck all along in my case.

What's the engine, original NCK/TVR Power 400? Or something else? Is that 218bhp at the flywheel or at the wheels?

I took 15mm off my trumpets and struggled to notice any difference, but my engine revved to the skies to start with. Dyno tells me it's not worth doing so with peak power and torque being low 5000s. Maybe I should glue a bit back on to the trumpets

[Transmitter Man]

My 2p based on my other V8 being recently on an engine dyno.

Cheapest horsepower gain was when we added a phenolic carb spacer. Gained around 7hp.

My dyno man suggested either phenolic, plastic, wood but not ali and the taller the better that would fit under the bonnet.

I'm sure I've seen these for the RV8 plenum's at around £38.00.

Also, I'm getting rid of my AFM with the Megasquirt.

I'd love to see just what pony increase if any with one of those rather expensive carbon trumpet / plenum kits.

Seems a great deal of money when one can just cut down the trumpets.

I want to see before and after numbers, not advertising spiel.

Phil
420 SEAC

[The Hatter]

Shorter trumpets will give more top end power but less low end torque. It's the torque that accelerates the car, not top end power... Not reving beyond 5k is a little strange though, I suspect something else is going on in that case.

Thanks for the run out in your car Jim, it's a fabulous machine...

Martin

[JMF894]

For the record, in case some don't realise it, mine is a 1989 450 flapper. It's an NCK/TVRPower engine with 74mm plenum intake ID. This engine revs freely past 6k. As The Hatter will testify

Glad you approve Martin. When a fellow (more knowledgable) wedger approve you know its gotta be ok

[Wedg1e]

Transmitter Man said:

I'd love to see just what pony increase if any with one of those rather expensive carbon trumpet / plenum kits.

Seems a great deal of money when one can just cut down the trumpets.

I want to see before and after numbers, not advertising spiel.

I suspect Tim Lamont and Mark Adams would waste rather less of their lives on carbon-fibre intake systems if there was absolutely no improvement to be had.

Interestingly, some (supposedly) pretty 'hot' RV8s (including the 390SE) run exactly the same injectors as the cooking 3.5L... and some with gaping throttle bodies make hardly any more power than those running the standard 72mm variant. So what percentage gain chopping or lengthening the trumpets is going to make in such circumstances is questionable.

[eesbad]

http://www.mez.co.uk/TuningTheRoverV8-pt5.html

For those who've not seen this site. The guy is a PH'er who goes under the nom-de-plume of 'eliot' (I think from memory!).

[Transmitter Man]

I have visited Elliot in Milton Keynes.

Nice chap and knowledgeable indeed.

Phil
420 SEAC

[B@man]

......he does a bloody good value 72mm throttled plenum too !!

I've done a few tests looking at the map sensor readings and at full throttle the map is showing atmospheric pressure even with my lawnmower spec K&N which to me indicates that whatever restriction is in the AFM, Filter and intake hose it's sod all. The standard hose will be installed in the bin in the near future as it looks terrible and I had to heat it up to get it over my Elliot modded plenum.

Edited by B@man on Thursday 21st July 11:53

[grahamw48]

Wasn't it the theory that a ribbed intake hose would disturb the airflow so that it would actually mix better with the fuel ?

There seems to be a definite lack of before and after figures for the various RV8 tuning options, so many of the commercially available 'upgrades' are pretty meaningless.

I thought the acknowledged restriction on this engine was valve size, and on the Wedge in particular, exhaust manifold design.

After optimising the above,I'd have thought that a Camshaft upgrade would be the next step, depending upon was was already fitted (and what state it's in).

Just getting the engine and it's ancillaries running cock-on will likely release anything between 10 and 50 bhp !

Edited by grahamw48 on Thursday 21st July 15:22

[adam quantrill]

I run a pressure gauge on my plenum and anything less than 95% throttle tends to give significant vacuum.
So do make sure your throttle cable is adjusted properly and the throttle opens fully.

[Transmitter Man]

I'd be interested to know whether any of the after-market or stock for that matter, exhaust manifolds were optimised for max torque with regards diameter and length of primaries.

If not there is I'm sure some free online software to design some?

I'd be interested in arranging some dyno time up at EDA (Castleford, Yorkshire) to do some parts testing on a wedge RV8 mule motor. Probably not important what size the engine is as far as A/B comparisons are concerned.

It would need a collection of donated parts (to be returned) and would be good to try out a bunch of heads, intakes and and exhaust manifolds plus a selection of cam profiles.

Anyone interested in this sometime during the winter when it will probably be easier to book dyno time?

That reminds me, must grab a pair of Buick heads.

Phil
420 SEAC

[honestjohntoo]

JMF894 said:

some suggest that replacing the standard plenum elbow with a smooth bore pipe such as silicone or polished metal may give a modest gain in power.

I think grahamw48 has it bang to rights.

Turbulating air will mix far better with the fuel molecules injected into the inlet tracts.

From there on fettling the intakes, best practice is to encourage the smoothest possible flow into the combustion chamber via the inlet valve area.

Everything prior to that - the more humps and bumps the better.

I did a bit of googling using word combinations like "turbulating intake air" and came up with a few patent references (out of literally dozens of them). viz:

---

• "Another of the features of the invention is the provision in the internal combustion engine of means for turbulating air flowing through the inlet which includes a plurality of deflector blades located in spaced relation around the periphery of the air inlet ..."

and

• "Means are additionally provided to cause turbulation of the air flowing through the air cleaner into the inlet end of the carburetor ... such turbulation of the air being provided to improve the mixture of the fuel and the air entering the engine ..."

and

• "More particularly, the turbulation means is intended to impart a rotary motion to the air flowing through the air cleaner ... to thereby increase the velocity of the air entering the carburetor and increasing the facility with which the air will mix with the fuel to produce the desired fuel mixture ..."

=============================================================================

So it seems there is something scientifically desirable in having a turbulated input airflow in some internal combustion engine applications to improve fuel/air mixing and apparently, airflow speed too.

In aerodynamic terms, turbulating air is much less sticky that smooth flowing air, indeed, model aircraft wings (low air speed applications) are designed in such a way to make air break away from the upper surfaces to speed up the laminar flow and reduce the pressure over the top of the airfoil section, enhancing lift.

Add to that the effect of "rough" air mixing better with the fuel it may even be that the proposal to make a smooth intake tunnel will reduce engine efficiency.

[grahamw48]

Well, I certainly prefer to 'turbulate' my coffee before slinging it down my neck.

Can lead to me back-firing sometimes though.

[Alexdaredevilz]

For all it's worth and any use to you guys

I added 45mm trumpets and manifold
Act elbow and induction kit
Full decat
MA chip I gained 30bhp and 10lbft
On a mild tuned 4.6 chimp

Edited by Alexdaredevilz on Friday 22 July 01:38

[grahamw48]

I gained 15bhp by having it twiddled with on the rolling road.(400SE)

My friend's 2.9 S series went from 99bhp to 172 bhp by having the throttle set to open fully, and a bit of gasket that was partially blocking the AFM removed, again on the R/Road

[B@man]

Interesting debate about the turbulating air prior to the throttle body but I have seen test results and various metal implements designed to do just this and the consensus is that the don't give any more HP or Torques (a bit like the e-bay electric "superchargers") Thinking about the plenum design on the RV8 as the air has to do a swift 90 degree to get from the TB into the intake trumpet and then do further directional changes before it gets near the inlet valve I really cannot see that anything prior to the dynamically complex plenum would make much of a difference. Other than a proper supercharger.....

Interesting issue !