ram tubes, worth getting??

[Lith]

Really bad turbo selection and/or installation.

My V6 turbo race engine pulls almost peak boost from 2700RPM (a little boost creap at 7500RPM) with two GT2871r's. It's currently pulling only 610whp on only 16PSI (IAT's too high). So if you're spooling at 4500RPM, you've got some serious issues.

No me, a certain Silver AE101 ex-NZPC covercar that showed up in HiOctane DVDs. I bet you a cheeseburger that if you put a single GT2871R onto a 4AGE you won't make 16psi anywhere near 2700rpm - I'd be more inclined to say your example shows how much better lb for lb your VQ35 is than a 4AGE than how poor the turbo match was, and on topic a bit... this is something of a testament to the old "no replacement for displacement" addage. When trying to get more torque everywhere, I'd weigh up going for a 7A bottom end... depending on how much quads cost.

[Mr Revhead]

If thats the car I think it was it was a pretty awful build!

[QikStarlie]

Really bad turbo selection and/or installation.

My V6 turbo race engine pulls almost peak boost from 2700RPM (a little boost creap at 7500RPM) with two GT2871r's. It's currently pulling only 610whp on only 16PSI (IAT's too high). So if you're spooling at 4500RPM, you've got some serious issues.

No me, a certain Silver AE101 ex-NZPC covercar that showed up in HiOctane DVDs. I bet you a cheeseburger that if you put a single GT2871R onto a 4AGE you won't make 16psi anywhere near 2700rpm - I'd be more inclined to say your example shows how much better lb for lb your VQ35 is than a 4AGE than how poor the turbo match was, and on topic a bit... this is something of a testament to the old "no replacement for displacement" addage. When trying to get more torque everywhere, I'd weigh up going for a 7A bottom end... depending on how much quads cost.

depends on trim of said turbo. quite a few different trims in the 71r. would think you'd be getting down to 3500'sh with the smaller one. i have full boost by 4000rpm on gt2876r on smallport. but yeh 2700 not likely.

as for the trumpets. don't bother unless you have an aftermarket ecu to tune with. afr will be all over the show.

[Dell'Orto]

If thats the car I think it was it was a pretty awful build!

My/Jeremy's old one. Definitely had room for improvement, but a VF23 is pretty big for a 1600 too

[MAGN1T]

i have full boost by 4000rpm on gt2876r on smallport. but yeh 2700 not likely.

as for the trumpets. don't bother unless you have an aftermarket ecu to tune with. afr will be all over the show.

What's "full boost"?

It's pretty meaningless if you're running 15 PSI.
then you turn it up, it'll come later.
As for ram tubes, the longer the better, you get less peaks.

Steve

[QikStarlie]

What's "full boost"?



Steve

cant run much, might blow head gasket being a toyota


also pretty meaningless saying longer is better. still need to tune the length to the rpm range your aiming for. will always be some compromise with a fixed runner

[strx7]

there is a good write up on a guy with a Neon who tried all sorts of different length tubes (from PVC from memory) and ran them all on the dyno, and what it showed is pretty much what was said above, the longer the tubes/runners the less peaky the torque curve is meaning broader power range. If i could fit 2 foot runners into the engine bay, i would have them.....

[RedMist]

there is a good write up on a guy with a Neon who tried all sorts of different length tubes (from PVC from memory) and ran them all on the dyno, and what it showed is pretty much what was said above, the longer the tubes/runners the less peaky the torque curve is meaning broader power range. If i could fit 2 foot runners into the engine bay, i would have them.....

It's been a while so forgive detail errors (large cc and turbo's in pairs make you lazy)
Optimal length, determined by helmholtz frequency, is massive (like 6 foot). As it's not easy to fit that amount of intake in a modern car, we use bounces of frequency 1/4 or a 1/5 the wavelength (and considerably shorter intake). That's why, while increasing your length, you'll exceed a certain length and then the helmholtz "free charge" will be back on the top end, or not visable (as you'll have to do 10,000RPM). So it is and it isn't true that longer runners make for a broader torque curve... hope I've confused myself sufficiently?

[strx7]

yeah say for instance you are making ram tubes for the F1 engine you just happen to have sitting around that likes to rev to 19,000rpm, then big long tubes will start to limit top end too much but for most engine us minions use that only rev to 8 or 9000rpm then long tubes for fatest midrange is where it is at

[MAGN1T]

The ideal length (valve to plenum) is approximately the same length as the ideal length for the primaries of the exhaust headers.
That's because it's the same theory. Just that the speed of sound isn't quite the same for them.
In real life the ideal length won't fit so a fraction of the ideal length is used which will give dips in the torque curve at certain RPMs.

Steve

[RedMist]

The ideal length (valve to plenum) is approximately the same length as the ideal length for the primaries of the exhaust headers.

Not quite. Velocites are different, cam timing, pipe diameter, even the volume (as you have burnt the O2 and fuel). My 4age ran a calculated 19 inch exhuast primary and 17.5 inchs from valve face to bellmouth. Not saying it's correct (as I didn't play on the dyno for hours and hours). It's just what calculated out on my engine.

[QikStarlie]

doesn't matter how long or short for that matter, still going to have peaks and dips. benefit of longer runner is the peaks will be broader. plus if you're able to make runners long enough to say catch the 3rd revision rather than the 4th. the peak will be stronger, but have less peaks across the range. but as redmist says, if you were just make them "long." may end up with a runner thats tuned for 2000rpm or 10,000rpm etc.. which would be useless.

an example on a turbo engine; we'll take a 4age. put a big turbo on, that comes on boost (20psi to make magn1t happy) at 5000rpm. factory inlet manifold is tuned for around the same. you get a massive torque increase when it come on boost. then shortly after torque takes a dive then power shortly after that. dead by 7000rpm. now, same engine install a shorter runner inlet manifold. turbo comes on nicely at 5000rpm no horrible surge in power. 6000rpm your shorter runner inlet manifold starts working and your good till 8000+rpm. with higher peak power (more cylinder fill at higher rpm) and broader powerband. you could do the same by using a longer runner manifold. but good luck fitting it under the bonnet.

[Flannelman]

At megameet last year someone performed a back to back dyno run using 50mm runners and stock ones on there blacktop 4age.

From a pure kW point of view, the 50mm made an extra 2-3kW more but it came at the expense of 3-5kW throughout the entire power curve. The extra power came in at the very top end (7700+).

To me, I wouldn't use them as the only benifit comes in above 7700 and sacrifices 3-5kW from 2000-7500. Since rev cut is around 8200, it gives a 500rpm band where they are an advantage over stock.

[1I1]

Yeah that was Rhys (togue_trueno) both made the same peak power figure

blue line is std, red line is TWM trumpets

[KinLoud]

My (unproven) theory about turbo's and intake length....

Longer runners = moves the peak torque to a lower rpm

peak torque at lower rpm = more exhaust gas at lower rpm

more exhaust gas at lower rpm = earlier turbo spool

earlier turbo spool = lower boost threshold rpm and lower max boost rpm

lower boost threshold rpm and lower max boost rpm = happier driver


Comments? Thoughts on my theory? (looking for structured and soundly argued comments vs yeah/nah)

Ken

[MAGN1T]

Redmist is confusing people as he's comparing a TT setup with a single turbo setup.
If you had 2 small turbos on a 4 banger then you'd get similar results.

The idea is to measure up some good factory manifolds and compare.
EG one N/A Mitsi motor that makes 90HP/Litre has intake runners approx 70cm from valve to plenum. Butterfly valves shorten it at maybe 4500 rpms to give 50 ish cm runners that take it out to 8K with a dead flat torque curve.

50cm? that's roughly 19 inches.

Steve

[QikStarlie]

My (unproven) theory about turbo's and intake length....

Longer runners = moves the peak torque to a lower rpm

peak torque at lower rpm = more exhaust gas at lower rpm

more exhaust gas at lower rpm = earlier turbo spool

earlier turbo spool = lower boost threshold rpm and lower max boost rpm

lower boost threshold rpm and lower max boost rpm = happier driver


Comments? Thoughts on my theory? (looking for structured and soundly argued comments vs yeah/nah)

Ken

see my theory few post back. na, alot of people say tune the inlet to the lower part of the power band, to create a board powerband.
on a factory turbo engine, you'l have boost coming on before the inlet comes in effect. which is great, nice smooth broad powerband. now with larger turbo standard inlet manifold, you get a narrow short power band that comes on hard, induces wheelspin, feels fast but isnt etc. if you were to tune the inlet below the turbo threshold, it would drive nicer cruising around. but throwing away power when on boost. inlet tuned above turbo threshold. refer to my other post.. going shorter you may even catch one of the weaker waves at low rpm, making the car better to drive off boost. i dont think trying to bring the turbo on with inlet tuing is a good idea. unless you have a variable setup like magnet speaks of

[RedMist]

Actually turbos are very hard to tune for Helmholtz. Because of the variation of density of the charge and the turbine blades tending to mess up the strict pulse needed for helmholtz tuning.

You're considerably better off matching the turbo correctly, using a divided manifold, looking for flow restrictions, minimising intercooler length, recirc blowoff, exhaust tuning, cam timing (VVT gives massive gains on my spool) etc.

My race engine takes a dip mid torque curve. However I suspect it's the abnormally small exhaust runners causing reversion. Something I can't change in my narrow offroader.

Ken's basic theroy is correct. If Helmholtz would make a difference to turbo spool or not... I suspect the latter.

[QikStarlie]

not a very good comparison at all. as different dynos and other changes were made, but shows what a different inlet can do. look at the torque curves. this is on a 4efte

standard inlet t3 turbo. not bad at all as turbo isnt too laggy
http://img.photobucket.com/albums/v178/ ... 0022-1.jpg

very similar setup. first attempt short runner inlet manifold. obviously bit too short for setup. felt like it came on boost twice. and would be down on midrange.
http://img.photobucket.com/albums/v178/ ... c_0083.jpg

2nd attempt inlet manifold. was not dyno'd with the above setup, but throwing it in here, as this one worked well with the setup. 5efhe bigger turbo, nice progressive power and drove real good off boost. could have done with more rpm to make most of the powerband, but was nursing standard rods
http://img.photobucket.com/albums/v178/ ... epdyno.jpg

make your own conclusions. but i think inlet tuning is bit overlooked on turbo setups

[RedMist]

Seems about face. The shorter intake runner appears to make more power mid range. I don't see it as a torque dip (which incidentally is only about 3% of total torque) more of a torque boost lower in the RPM range.
My bet is that it was faster through the RPM range with the shorter intake.

As you know comparing dyno runs is difficult without very quantifyable changes.. and the same tyno.