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The idle rpm is rock solid, especially for a somewhat hot-rodded engine. Certainly the new MAFs seem to be working well. The idle vacuum is a constant between 15-17 Hg, the vacuum level depending on the environmental conditions. This with eighty pound injectors and 32 year old EZ-K and LH (reprogrammed by Niklas).
It’s made 862 rwhp since the video was shot, which is close to 1k at the crank.
The next step may be a thorough inspection of the engine internals for two reasons. First, the broken vacuum line run was lean, and the results of that needs to be known. Second, it’s now clear what the engine needs to do in order to make a lot more power with this driveline, namely the engine needs to be run at much higher rpms. One may need to strategize now how to get to those higher rpms safely.
It’s made 862 rwhp since the video was shot, which is close to 1k at the crank.
The next step may be a thorough inspection of the engine internals for two reasons. First, the broken vacuum line run was lean, and the results of that needs to be known. Second, it’s now clear what the engine needs to do in order to make a lot more power with this driveline, namely the engine needs to be run at much higher rpms. One may need to strategize now how to get to those higher rpms safely.
If this motor is still using the heavy stock rotating assembly, 6800 rpm is the upper limit , correct?
would a bore camera be sufficient to inspect for detonation damage on these durable pistons?
If this motor is still using the heavy stock rotating assembly, 6800 rpm is the upper limit , correct?
Yes, I think that that’s the limit for the stock rotating assembly, around there at 6800 rpm.
In terms of the near stock engine, this 862 rwhp is likely the limit. If the personal science project is to proceed further, we need to make bigger changes, either to the rotating assembly or the transmission and clutch, or both.
Right now, nothing will catch any of those when the car is driven on the street.
AF gauge based on a single post-turbine WB02 sensor wouldn't catch any of the above, if the pre-turbine heat and pressure are such that the mixture burns in the exhaust manifold.
The Q1 2020 project is to install a separate data logging system with sensors to see what is going on with the engine when it's being driven on the street in various conditions. After we are seeing those data in sufficiently large samples, we can start thinking of problem conditions and how to detect them without too many false positives.
You should seriously consider switching to an aftermarket ECU which can datalog, control individual cylinder tuning for both fuel and timing, set up safety overrides to kill ignition when preset parameters are met (excess boost, EGT, cooling system overpressure, knock sensors, whatever you want) , etc. I run Holley Dominator ECU on both my cars and it is quite capable and logs EVERY single channel EVERY time and is self tuning based on O2 sensors. Not to mention you could run Coil on/near plug as well and it has traction control built in as well as boost controller. I even replaced the stock gauges with their digital dash.
Wossner pistons are alusil compatible and something like 60g lighter than stock per piston, and they come in 100.5, 101, 104mm or whatever you want. About $2000 for a custom set of 8.
Molnar makes an Hbeam rod for the 944, about 200g lighter than stock iirc, for $420/set of 4. You'd need them shaved on one side to fit the 928 crank.
A few places in the US have jigs to modify a 928/944 conrod to use a Clevite performance rod bearing which will hold up much better than stock Glyco... about $300 for a set of 4 rods for the machining and the bearings are for a Toyota i think so they're cheap and available.
Just figure your oiling and breathing...
Contact user michaelmount123, he has the recipe for reliable 8000rpm 944 dohc motors, most of which is transferrable to the S4. He did a 3.2L engine for a guy in Thailand that made over 400 crank hp N/A.
Originally Posted by ptuomov
Yes, I think that that’s the limit for the stock rotating assembly, around there at 6800 rpm.
In terms of the near stock engine, this 862 rwhp is likely the limit. If the personal science project is to proceed further, we need to make bigger changes, either to the rotating assembly or the transmission and clutch, or both.
Wossner pistons are alusil compatible and something like 60g lighter than stock per piston, and they come in 100.5, 101, 104mm or whatever you want. About $2000 for a custom set of 8.
Molnar makes an Hbeam rod for the 944, about 200g lighter than stock iirc, for $420/set of 4. You'd need them shaved on one side to fit the 928 crank.
A few places in the US have jigs to modify a 928/944 conrod to use a Clevite performance rod bearing which will hold up much better than stock Glyco... about $300 for a set of 4 rods for the machining and the bearings are for a Toyota i think so they're cheap and available.
Just figure your oiling and breathing...
Contact user michaelmount123, he has the recipe for reliable 8000rpm 944 dohc motors, most of which is transferrable to the S4. He did a 3.2L engine for a guy in Thailand that made over 400 crank hp N/A.
-60g relative to stock S4 piston weight isn’t going to cut it at high rpms. Wossner 944 pistons don’t have ring widths that work with high rpms. Nobody has been able to get any aftermarket coatings to run reliably on 928 block alusil, including Wossner’s. H-beam rods are not something that I’d want in a turbo engine.
-60g relative to stock S4 piston weight isn’t going to cut it at high rpms. Wossner 944 pistons don’t have ring widths that work with high rpms. Nobody has been able to get any aftermarket coatings to run reliably on 928 block alusil, including Wossner’s. H-beam rods are not something that I’d want in a turbo engine.
H rods should be more suited to your revs goal than an I-beam type, I believe?
and Wossner will cook you custom pistons any way you like, fat rings or whatever, for that price.
H rods should be more suited to your revs goal than an I-beam type, I believe?
and Wossner will cook you custom pistons any way you like, fat rings or whatever, for that price.
Originally Posted by Thom
H-beam rods have been used successfully on 3L+ 944 turbo engines with nearly twice the specific output of your engine.
It's a hobby science project for me, so we're just going to tinker with it based on our understanding of the engineering that we have. I-beam and H-beam are about equal under tension, and H-beam is cheaper to fabricate in small series. That's why normally aspirated aftermarket "performance" rods are usually H-beams, there's logic to it. I-beam is generally stronger under compression than H-beam, so that's why turbo diesels usually use I-beams even when the series is relatively small. So it's more the principle of it. In practice, the power levels and cylinder pressures for these old engines are so low that it doesn't probably matter in practice.
After the fuel pressure vacuum line failure, John is going thru the engine with a fine toothed comb to find any issues. So far, no problems detected. Leak down and compression tests done, photography with boroscope next, then running it with the blow by meter hooked up.
Numbers within measurement error where they were when the blue engine was installed:
The leak down numbers are literally equal within measurement error. The supply pressure was set to 94 psi. One helluva engine, someone got the ring gaps right. Oh wait, gapless...
09-28-2019, 11:30 AM
The idle is rock solid.
