Fresh GTS engine with GT cams, dyno
#16
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I customarily publish both rear wheel HP and engine HP, and I did so here. You can use whichever number you want.
The reason for posting engine HP numbers is because the RWHP number was never published by Porsche. So, if a person wants to know how much more HP they have gained over stock, they have to calculate the BHP so they can compare it to the published engine HP.
The reason for posting engine HP numbers is because the RWHP number was never published by Porsche. So, if a person wants to know how much more HP they have gained over stock, they have to calculate the BHP so they can compare it to the published engine HP.
#19
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Interesting Hot Rod article drive train losses may be more than you expect.
We do a lot of baseline dyno pulls before we supercharge a car to make sure all is at it should be. And I have to say, time and again, you take the RW number and add 15% and you land dead nuts on Porsche's published HP numbers.
So, for us, the 15% drive ttrain loss on the G28 transmission is very many times confirmed for me.
Then later, I found out I was doing the math wrong. I was simply taking rear wheel X 15% and adding it on. That's wrong. Somebody here that knows math a lot better than I do showed me the right way is RW number divided by .85 = Engine.
Thats what I use now.
Last edited by Carl Fausett; 06-07-2019 at 04:13 PM.
#20
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Must say my "thanks" to John Speake of JDS Porsche: thank you for your excellent and quick service. Sent John the LH, EZK, and the MAF sensor from this car after we had put it all together and the GTS map wasn't happy with the GT cams - lumpy idle. John found the hot wire sensor was off calibration and fixed it, and he modified the GTS's low idle to produce the higher idle that is needed for the GT cams.
The parts came back in about 10 days round-trip, went right in, started right up - idles great and runs nice.
Thanks John!
The parts came back in about 10 days round-trip, went right in, started right up - idles great and runs nice.
Thanks John!
#21
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Teamwork!
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#23
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Hi Carl - about to do the same to my 93 GTS - pull the engine and drill the pistons - Why did you replace the pistons? If it is a trade secret I understand but I do not plan on replacing the pistons and did know you had to.
I am replacing the rods because mine has the weak rods.
OK I see why as you opened the bore slightly - forget I asked - sorry
I am replacing the rods because mine has the weak rods.
OK I see why as you opened the bore slightly - forget I asked - sorry
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
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928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
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#24
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My GTS has covered over 170k now. Having seen a few GTS heads and pistons during rebuild I wanted to remedy the oil ingestion once and for all. The build up of carbon is alarming to say the least and the resultant effect on timing (up to 9 degrees) is bringing the power down.
Many GTS engines were rebuilt by the factory if oil consumption was below 500 miles per Liter IIRC.
Many GTS engines were rebuilt by the factory if oil consumption was below 500 miles per Liter IIRC.
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(Of course, all the GTS pistons come without the holes drilled.)
#28
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Seems overly "optimistic" for a simple displacement change (although it does run like a scalded cat .) Therefore, I "used" an more conservative 1.125% factor, when talking about it, which is what I generally use for a manual. (I use 1.2% for a manual.)
I can do it your way, makes no difference to me.
What do you want to use for an automatic?
#29
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What we've found by varying boost etc. is that a reasonable approximation for a 5-speed manual 5.0L 928 S4 might be obtained from the following formula:
Flywheel hp = 10 hp + rear wheel hp / 0.88
It's not the truth but seems to match our data reasonably well as a crude approximation. Wide standard errors, of course. It's obviously not a valid formula for zero or 10000 rwhp.
Flywheel hp = 10 hp + rear wheel hp / 0.88
It's not the truth but seems to match our data reasonably well as a crude approximation. Wide standard errors, of course. It's obviously not a valid formula for zero or 10000 rwhp.
#30
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