Adam Mowafy

I was wondering how well Audi balanced this engine? I remember someone saying they had their redline at 7500 rpm's. Would having the crank balanced achieve that? Just curious how people have raised the redline that much without damage?

Toxcheap

I don't think you'll have any balancing issues below 8000 rpm. But you'll be so off cam it wouldn't continue making more power. My brother has rev'd a 10 valve higher than any one before (I'm guessing) without any flying out of it (luckily!!!)
You see he was at 90 or so and went for forth and found second. The clutch didn't slip, the diffs were locked and smoke was coming from the tires. And the tach was pinned like you woulndn't image!

It's funny now,
But it wasn't then!
LOL
TOX

1 slow Audi

That hapened once so it took it but I dont think that it would take it for a longer time period.
If u planing to go more than 500rpn above stock red line you should.

Toxcheap

You think so, we hold that motor at 7200-7500 rpm staging at 23-26.5psi of boost. I once was told that VW/Audi would set redline at 1000rpm be low actually redline to improve longevity.

Adam Mowafy

I hardly ever take it up that high, because the car seems to lose power after 5500? I'm just curious thats all.

Toxcheap

Who's software are you using?
As for the power rolling off at 5500 that will happen if the cam timing is slightly advanced, low fuel pressure, high control pressure, bad plugs, wasted cap, boost leak, and so on.
Sorry I can't be more specific.

HTH
LATER
TOX

shortyq

A couple of things. First, this is where a dyno might help. The I5 10v t/na intake manifolds are tuned to provide peak power at 5500-5700rpm. You can do a LOT of tweeks to the I5, and still get peak power and peak torques pretty much where the factory has them, btdt. To increase the rpm of peak power, you need to change the intake system. Changing the exhaust system tends to hold peak power longer before falloff, but doesn't really change it's peak.

Cams tend to move the VE of engine power higher in the rpm range, and can effect rpm peak power, but not really all that much IME. Cam timing rarely affects peak power rpm, but can massively affect VE at higher rpms.

All that said, the other reason you don't want to run much over stock redline on a 10vt is valve float. The hyrdraulic lifter cams tend to suffer valve float above 6500, but with stiffer springs can run around 6900 without problems. Beyond 7000 Audisport uses mechanical lifters. I've installed ti valve trains to raise the 10vt limit, but it's expensive. The 20vt uses 4 valves which are lighter, which allows for higher revving (the IM on the 20vt also moves the rpm peak power to 5900rpm)

Why run over stock redline? Well, in the case of 1/4 mile guys, that extra rpm may result in a better time/ET because you might be better matching the torque band between shifts. However, properly matching shifts to gearing can address this problem better than stressing the stock engine components. Or switching to an early style (pre 85) solid lifter head with mechanical lifters can also more safely address higher revs.

HTH

Scott Justusson
QSHIPQ Performance Tuning

Adam Mowafy

I havent driven the car since the upgrades so I'm not sure how it is now. But I had a leak in the intercooler endcap, it's fixed now. would that make a considerable loss of power at high rpm? I'm guessing yes, more air flowing but alot is leaking out under boost right?

Toxcheap

I've got some different opinions. Intake manifold design although important isn't quite as noticeable on a turbo motor versing a NA motor. NA motors resonance tuning is important because the motor is drafting it's own air, so tuning the manifold's resonance frequency increases its efficiency. The longer the runner the lower in the band you tune and the shorter the higher.

Turbo motors on the other hand are being force feed air so manifold changes actually change the compressor's map vs RPM. And on the subject of cam timing, boost onset and peak power rpm are tremendously affected. Our experience is if we are on a tight course advancing the cam lowers rpm of boost on set there for increasing low rpm torque and helping the car get out of low speed turns faster. But the motor runs out of puff at 5400 rpm (roughly) which would kill you on the 1/4 mile. Retarding the cam puts peak hp back in the mid 6000 range which is good for 1/4 mile because your hopefully never in the lower range.

Don't mistake what I'm saying. I'm not adding or subtracting any power I'm just moving the slope and peak up and down the rpm range.

As for mechanic lifters: Great on a race car, huge intercooler, stand alone engine management, lots of cooling and consistent power. Meaning you won't lose valve lift (or a race)if your hydraulic lifters pump down because of detonation. But on a street car that relies heavily on its knock sensor it's a terrible idea. Mechanical lifters create so much noise it renders the knock mic. useless. And this is just my take on it. It all comes down to what will work for you. And building a new intake manifold on a slightly modified 5000 to increase peak power rpm seems like effort put in the wrong place.

HTH
LAter
TOX

shortyq

Toxcheap:
Be careful of what you are claiming here. Remember, in a 10v cam, you change the cam timing on the intake lobe, you change it on the exhaust lobe as well. As a rule on the 10v cars, if you advance cam timing, you have increased the amount VE at lower rpms, but decreased the amount of VE at higher rpms. This is similar to raising the compression ratio. Up to a point. The reason the hi rpm losses occur with cam advance is because the exhaust valve (duration) is closing sooner than it needs to to more completely purge exhaust. Double edged, you lose VE AND you lose exhaust energy by definition (>reduces turbo efficiency).

If you retard the timing, you increase the amount VE at higher rpms, where cam overlap really isn't a problem anyhow. Overlap isn't a problem in a turbo car at high rpms because you are using turbo Pressure to help purge the combustion chamber. You increase the pressure of the turbo, the delay in the intake valve opening isn't a huge factor.

Overlap on turbo cars is an issue in low rpm. For instance, the 272 schrick is a great cam for the 10vt (highest lift of stock available cams)in racing and hi rpm applications, but it's overlap makes for a very lumpy CIS idle, and the overlap is noticeable in midrange (you get to 10psi quickly, but the overlap blows thru to the turbo). This is a volumetric efficiency equation (the increased overlap decreases effective compression ratio), not a intake manifold one. Massive increase in HC too, because you have very inefficient combustion at low rpms (your effectively blowing it right out the exh valve)

To gain the benefits of SOHC timing, you need to change the relationship of the intake to the exhaut valve opening/closing. This isn't possible with a 10v cam gear by design. So you play a game of give and take. IME (10vt cam gear in 1992, a plethora of cam installed from 268/272/276/300 to ABT), audi has their cam gears pretty well dialed in to get the minimum HP/Torque compromises.

I think if you take a moment to gander at some adj cam gear dyno sheets on the internet, you will find cam timing gives very little difference in rpm as far as peak hp and peak torque. Change that intake tract TO the valve, even audisport has made massive changes. Well documented in racing (or just compare the RS2 to the 3B IM)

WRT mechanical lifters causing knock sensor anomolies, I haven't seen or heard about it. I have seen and heard this affected by the cam lobe vacuum pumps in 10vt conversions to n/a cars.


HTH

Scott Justusson
QSHIPQ Performance Tuning
Chicago