3.0 16V engine mods, etc

[Thom]

Stock harness and a Bosch 044 pump. I had already forgotten that the tuner had also suggested to monitor fuel pressure so thanks for bringing this up. He seemed pretty sure that the injectors were working harder than they should to cover for a loss of pressure.

[Tom]

Stock harness and a Bosch 044 pump. I had already forgotten that the tuner had also suggested to monitor fuel pressure so thanks for bringing this up. He seemed pretty sure that the injectors were working harder than they should to cover for a loss of pressure.

Does the ECU monitor fuel pressure? I go about 500/500 on a dynojet in the heyday of my 3L, using an 044 pump and Injector Dynamics 1300's at about 24psi. That's with the 8 valve head though, so I think you're right that there's something left on the table. I subsequently ran my own relay-triggered harness to the pump, after mysteriously burning a few out. I'll do a separate post on the details for that in the next few days...

[Thom]

The ECU does not monitor fuel pressure but I have to check how to do that, assuming I have any analog input left.

The peak power figure does not matter much, to be honest. The way the 16V engine runs is so much nicer than the 8V. Most people only see figures but what matters never shows on a dyno spread sheet, apart from the shape of the torque curve.

[SirLapsalot]

Back from the dyno... 517 hp / 529 lbs.ft (718 N.m) @23 psi.


240420_Dyno_SS.jpg


(First run was at 20 psi (1.4 bar) of boost, the other two at 23 psi (1.6 bar). On the very first test runs the engine was overboosting to 30 psi which triggered the MAP limit so had to adjust on the fly the boost table to clear things up, whence that first "clean" run at 20 psi)


240420_Dyno_log.jpg


The tuner said I should redo the harness to the fuel pump as the power should be much higher than that with such high injector duty cycle values with 1200cc injectors. He also reckoned that the 0.82 A/R turbine housing was too small for a 3L engine. The loss of power above 6000 rpm as shown on the spreadsheet is not anywhere near as obvious on the road, though back pressure may be climbing fairly steadily above 6000 rpm.

The bottom line to me however is the plateau of torque of more than 370 lbs.ft (500 N.m) from ~3200 to ~6500 rpm which I hope illustrates a bit better what I meant about this set up being really good on the road.

Looks like HP and TRQ don’t cross at 5252 in that plot? Torque curve looks super nice though. Gotta be lots fun on the road!

The tuner you reference, are they actually tuning or just running the car on the dyno?

[Thom]

The curves don't cross because torque is here measured in N.m.
The tuner/dyno owner works mostly on VAG cars and in this instance he just floored the throttle as I just wanted to get a basic idea of where the engine "was". There is some homework to be done before considering going back there. At least I can say that it may only be on the dyno that the engine will see such load as anywhere else on the road under the same conditions I get loss of traction. The rear end did bounce a little on the rollers despite the car being strongly strapped to the ground. The shop mechanics seemed impressed with the performance as they left what they were doing to check what was going on in the dyno booth.

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Ps : as a side note I was impressed but not in really positive way that all the folks there were about 45+. I had expected to see youngsters aged 20 something considering this was an Audi specialist dealing with modern cars... Where are the young car enthusiasts gone? Are there even any?? Even though I am pleased with how my car performed the impression that there seems to be farffewer younger folks these days interested in that stuff leaves a strong bitter taste.

[Tom]

Different country, same issue. I haven't been to a dyno in several years, but back when I was trying to dial-in (dial-up?) my motor, I went to quite a few dyno shops in the area and never found one I really liked. One place had a dyno easily 10 feet in the air, with a lift platform that took the car up there so you could back the rear wheels onto the roller. Flooring a 500hp car while staring off the edge of a 10 foot platform took a pretty big leap of faith...

I see multiple clamps on the I/C pipes. If that's an issue, one of the best things I ever did on my motor was install "boost braces" that hold the pipes to the i/c. I initially put a clamp around the pipe with a strap attaching it to a screw along the front of the header panel. It looked awful but worked great -- never had a pipe pop off -- but I subsequently welded attachment points to both the intercooler and i/c pipes to fit .commercial boost braces. It's a completely fool-proof way to keep i/c couplers from blowing off. I had actually picked up Wiggins Clamps and intended to install them in due course, but the boost braces proved more than enough for my car.

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[blueline]

The curves don't cross because torque is here measured in N.m.
The tuner/dyno owner works mostly on VAG cars and in this instance he just floored the throttle as I just wanted to get a basic idea of where the engine "was". There is some homework to be done before considering going back there. At least I can say that it may only be on the dyno that the engine will see such load as anywhere else on the road under the same conditions I get loss of traction. The rear end did bounce a little on the rollers despite the car being strongly strapped to the ground. The shop mechanics seemed impressed with the performance as they left what they were doing to check what was going on in the dyno booth.


DSC_5577.JPG


Ps : as a side note I was impressed but not in really positive way that all the folks there were about 45+. I had expected to see youngsters aged 20 something considering this was an Audi specialist dealing with modern cars... Where are the young car enthusiasts gone? Are there even any?? Even though I am pleased with how my car performed the impression that there seems to be farffewer younger folks these days interested in that stuff leaves a strong bitter taste.

While not specifically addressing the shortfall you mention, there is some hope for that type of thing, at least in U.S.

https://www.hagerty.com/media/never-sto ... n-dollars/

https://www.hagerty.com/media/news/mcph ... endowment/

https://www.hagerty.com/media/events/ho ... en-budget/

[Thom]

Thanks @Tom.
The dual clamps up front serve 2.5 purposes :
- rubbing against the headlight bar instead of the IC pipe/hose ;
- they are spares if another clamp fails elsewhere ;
- I like the look with 2 clamps. It makes for a somewhat balanced appearance with the 2 clamps on the throttle body hose.

Since running the breather to atmosphere it seems the oil film in the inlet path has drastically reduced and the little amount remaining may only be what the compressor may be letting out through its seals. I am pretty sure that an excessive amount of oil deposits in the inlet path caused IC hoses to sometimes blow off on the 8V engine, and coupled with a small-ish air filter and the breather connected to the intake, is necessarily going to bring down the octane level of the mixture thus the knock threshold - in restrospect I am wondering if such a scenario did not prevent me to make the most of the 8V engine - getting 500/500 out of it always felt out of reach as running any more than 18 psi caused it to knock right away and lowering the timing felt counter-productive.

[Tom]

Thanks @Tom.
The dual clamps up front serve 2.5 purposes :
- rubbing against the headlight bar instead of the IC pipe/hose ;
- they are spares if another clamp fails elsewhere ;
- I like the look with 2 clamps. It makes for a somewhat balanced appearance with the 2 clamps on the throttle body hose.

Since running the breather to atmosphere it seems the oil film in the inlet path has drastically reduced and the little amount remaining may only be what the compressor may be letting out through its seals. I am pretty sure that an excessive amount of oil deposits in the inlet path caused IC hoses to sometimes blow off on the 8V engine, and coupled with a small-ish air filter and the breather connected to the intake, is necessarily going to bring down the octane level of the mixture thus the knock threshold - in restrospect I am wondering if such a scenario did not prevent me to make the most of the 8V engine - getting 500/500 out of it always felt out of reach as running any more than 18 psi caused it to knock right away and lowering the timing felt counter-productive.

My motor -- which if I recall is a near clone of your old one -- is prone to knocking too. I've managed to keep the head on with less timing, e85 or high octane, water/meth injection, strong spark, etc. but that's a lot of work, so lately have been driving it around at 16-17psi. I have a catch can, which helps, but probably not as much as having it open to the atmosphere. The oil can't help for sure, but I've always figured the pistons were the root of the knocking issue. Despite advertising and labeling, they work out to nearly 9:1 compression, which doesn't sound like much these days, but is pretty high for that motor and engine management. The early 930's had a 6.5:1 CR for comparison...

[Thom]

Don't quote me on this but I think I remember official documentation listing 968 turbo S/RS specs mentioning the S had a compression ratio of 8:1 and the RS had 7.5:1... With as much as 9:1 on our 8V engines the only way to free up some more power would have been major head work and a suited cam profile, as had shown Corleone with his exotic 3L 8V build. Just like Duke's first 3L 16V engine (9.5:1) they were both fast without necessarily making gobs of torque, which at this stage of understanding and experience I would think may be far easier to get with "high" boost levels and a "low" compression ratio. This is basically how I specced my 16V engine - Off boost it "feels" slower than the 8V (as thanks to the lower CR it is not "cumbersomely" quick when I want to drive it sedately), but may actually be just as quick whilst feeling pretty much effortless. Air velocity through the larger intake runners and inlet ports will necessarily be lower at small throttle openings than on an 8V engine. Air flow vs air velocity make for different driving experiences that in my opinion do not really show on dyno sheets, except perhaps if plotting the boost level vs RPM - since boost is a more or less direct measure of restriction and if we assume a turbo sized "properly" for a given engine, then perhaps the term "flow lag", to emphasize on the time it takes to reach peak boost may be more appropriate than "turbo lag". The 8V set up is so much flow-limited that trying to reach peak boost as early as possible in the rev range to widen the usable/fun torque band is always going to be somewhat of a big deal, or at least it was for me considering how much of a relative dead end the top end looked.
The trade off with the 16V engine is the slightly numb response down low, but you quickly learn your way around this by opening the throttle progressively, squeeze it rather than just flooring it down low, like on an old-school GT with a long throttle travel. Depending on one's application however this can be a minor give away, as if this reciprocally makes for an "exciting" sudden rush of torque when the cams kick in I find this preferable over the 8V's quicker torque build up for drivability reasons with an all-season road car. If it just takes shifting down and flooring the throtte to get nearly instant peak boost and risk losing traction then all for the better as far as I am concerned - less torque down low but so much more up top and on a wider range with an engine that feels so much "alive" up top. I also believe that making a "high" amount of torque down low puts more "inefficient" load on everything - more side loads on cylinder, bearings, transmission, etc, and this should affect longevity, So far so good with my modified 968 transmission at least, touch wood...