Twin Turbo 928 fixed and back out there terrorizing the streets!
07-26-2010, 02:12 PM
#241
Rennlist Member
The maps you have are correct. Those "special maps" were developed when Louie was tuning that twinscrew car with Sharktuner Mk1. and a SMAF.
With ST2 that you are using for tuning, the SMAF extended load files are a standard menu option.
Looking at the datalog you sent me , the load values look normal. When you first hit 100% load at 3750rpm, I reckon you are making about 540HP crank... !
With ST2 that you are using for tuning, the SMAF extended load files are a standard menu option.
Looking at the datalog you sent me , the load values look normal. When you first hit 100% load at 3750rpm, I reckon you are making about 540HP crank... !
I am still running at the single mode high up, so there's some extra headroom there. Not a huge amount, since the injectors still need to be closed a large enough fraction of the time to cool down, but one definitely gains half the injector opening/closing and fuel acceleration times.
Here's another question that I am trying to figure out. With the superMAF, how is the EZK load variable related to the LH MAF signal? The "EZK Load [%]" pegs at 100 before 3450 rpm and stays there for the duration up to the rev limit. Is that supposed to happen when the "LH MAF signal" is still showing a lot of variation in the range 160-225?
[EDIT: Some extra info here on superMAF EZK behavior: https://rennlist.com/forums/5308293-post12.html. Do I need the special EZK maps, too?]
Here's another question that I am trying to figure out. With the superMAF, how is the EZK load variable related to the LH MAF signal? The "EZK Load [%]" pegs at 100 before 3450 rpm and stays there for the duration up to the rev limit. Is that supposed to happen when the "LH MAF signal" is still showing a lot of variation in the range 160-225?
[EDIT: Some extra info here on superMAF EZK behavior: https://rennlist.com/forums/5308293-post12.html. Do I need the special EZK maps, too?]
07-26-2010, 02:22 PM
#243
Nordschleife Master
Thread Starter
My guess for the static compression ratio is 9.4:1, given the dish sizes I've seen / heard about for other '87 engines.
07-26-2010, 02:26 PM
#244
Nordschleife Master
Thread Starter
That would be about 750 ft-lb of crank torque. I doubt it's making that much at 14 psi. The rear wheel dynojet number from the 14 psi pull was 617 ft-lb, and dynojets show overly optimistic numbers.
07-26-2010, 03:04 PM
#246
Rennlist Member
07-26-2010, 03:37 PM
#247
Nordschleife Master
Thread Starter
Once you get much past 50-60lb injectors you are dealing with low impedeance injectors. Low impedance injectors can be drilled down to a much lower pulse width due to a faster reaction time, which is a direct result of how much current it takes to drive them. The 80lb (or larger, cannot remember) injectors Todd is using with Autronic are low impedance.
Some claim you can install a simple resistor pack to use low impedance injectors with a high impedance driver like the LH. Even if this were true, the stock system isn't going control them properly. A true low impedance system is "peak and hold", high impedance systems are known as a "saturated" system.
There are secondary controller packs designed to go between a stock high impedance system to properly drive low impedance injectors. I have yet to find someone that's actually attempted this on a street car.
Has very little to do with age since all 80-84 US L-Jet 928's have low impedance injectors.
Some claim you can install a simple resistor pack to use low impedance injectors with a high impedance driver like the LH. Even if this were true, the stock system isn't going control them properly. A true low impedance system is "peak and hold", high impedance systems are known as a "saturated" system.
There are secondary controller packs designed to go between a stock high impedance system to properly drive low impedance injectors. I have yet to find someone that's actually attempted this on a street car.
Has very little to do with age since all 80-84 US L-Jet 928's have low impedance injectors.
I don't know yet. What I do know is that the bottom of the intercooler is warm but the top of the intercooler is about the same temperature as the outside air. Which is not very scientific but seems to be indicating that the ICs are working. More data later.
For the record, I don't think I am making 750 ft-lb at crank at 14 psi. But we'll see. I am very interested in seeing what John's system can really do on a completely stock '87 long block.
07-26-2010, 10:48 PM
#248
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I just scanned through this. (I can't spare the time to read carefully and contemplate.) But,...
... nice job Tuomo. You have the meanest 928 on the East Coast.
... nice job Tuomo. You have the meanest 928 on the East Coast.
07-26-2010, 10:52 PM
#249
Nordschleife Master
Thread Starter
07-27-2010, 01:31 AM
#254
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Scary, scary, scary. Amazing system. A tribute not only to John's system but also to the 928 engine! Simply amazing. Makes all those no sayers second quess what is possible.
07-27-2010, 09:54 AM
#255
Nordschleife Master
Thread Starter
3500-6500 rpm on first gear feels like a blink of an eye, on second gear 4000-6500 takes about as long as it takes to think "remember to shift right away!" On third gear, there are several seconds to look around at the traffic and speculate if you hit anything on the first two gears.
Gauges are completely useless, other than the tachometer. I can't look at boost, I can't look at turbo speed, I can't look at the ST2, I couldn't look at the AFR gauge if I had one, etc. Even tachometer is a stretch. I now understand why people have shift lights. This all reinforces my view that audio alerts are going to be very important.
Gotta do something about the exhaust before the audio alerts would work, though... ;-)