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What is the assumed horsepower percentage loss used to arrive at the 100% driveline efficiency adjustment?
The 100% driveline efficiency is just the test mode that we use within the dyno software. This mode was recommended by Dynostar upon installation so we have used it for all tests since that day.
The engine hp figure is derived by adding the driveline rolling losses (measured during the coastdown from max rpm in the test gear) to the wheel hp, the final figure then adjusted by the DIN correction factor.
The DIN cf is calculated from ambient air temperature, pressure and relative humidity, all measured by the integral dyno weather station.
Thought you guys might find these dyno graphs interesting.
In the shop at the moment is a 993 Carrera 4S with Porsche upgraded X51 engine which we have just prepared for the new owner. Described by the vendor as:
"1996 993 Carrera 4S with the rare X51 3.8-litre Performance Kit Exclusive engine upgrade - in other words, it has a 993 RS engine. Capacity went from 3600cc to 3746cc thanks to an increase in bore from 100mm to 102mm and RS cylinder heads to match. Combined with reprofiled camshafts, a revised DMS control and a rigid alternator drive, this raised the power of the Varioram engine from 285bhp at 6100rpm 300bhp at 6600rpm. Torque went up from 340Nm at 5250rpm to 355Nm at 5400rpm. It was an expensive upgrade and, as such, only a handful of 993s in the UK were so-equipped, which makes this a very rare Porsche."
Fair enough? No....
As ever at Ninemeister, it's always better not just to take someone else's word for it when it comes to engine performance, so with the new owner's permission we disconnected the 4wd and ran the engine up on the dyno. The initial results were very disappointing but that was quickly traced to a bad batch of fuel, so once refilled we ran it up again and found potential issues with the operation of the variorum and resonance flap. Suffice to say we thought we could do better with a remap, so here is the before/after result with remap showing the difference when the intake system is working correctly. Final result was 320hp and 282lbft (382Nm), which is about as good as it gets for a remapped factory RS engine.
Outstanding. What exhaust and cats were on the car at testing? Stock airfilter? Anything else not stock but programming?
Where it gets more interesting (in my opinion) is when you compare the result to the equivalent 9m 993Vr +3, a similar 3.75 litre engine with 9m billet heads, 9m Sport cams, 9m modified stock Vr intake with 100 cell cats and remap. In this application the high velocity ports of the 9m head significantly out-perform the large port, high flow, low velocity 993RS head, increasing the VE (volumetric efficiency) right across the rpm range which increases the peak torque from 282lbft (382Nm) to 326lbft (442Nm) at peak. That's a huge difference.
I can (barely) understand why the RS head was made for homologation reasons, the engineers probably thinking they would need huge 46mm intake ports (stock 993 are 43mm) to achieve their performance objective for the RSR, but when you relate this dyno comparison to the X51 engine, it still puzzles me why Porsche specified the RS head for the kit. I've always been convinced that the stock Vr heads on a 3.75 engine with RS cams would achieve the same power but with more mid range torque, the good news is that sometime towards the end of January we will be testing that exact combination. Naturally the resulting dyno graph will be interesting in more ways than one and might save someone a fortune if they are contemplating the X51 conversion for their 993 and also question the logic of new cylinder heads.
The new 9m built engine is built and ready to be installed in a 993C2 that has undergone a full body restoration and which is currently sat in the build shop waiting on new suspension and the engine. More on this as soon as the 993 is finished.
Agree and have seen zero gain from RS heads. Rothsport build and dyno' approx 10 3.8 VRAM motors with RS cams. All had Giac or Wong chips, similar exhaust. The engine run on their in house engine dyno. Two real M64/20 motors were run, mine from a 993RS made 301hp with full stock including exhaust. Another had programming and the typical hot rod exhaust for use in early cars made just shy of 310hp. The balance of the engines used stock heads but with RS valves....all as strong or stronger than the RS head motors. The strongest was 324hp another of mine in an early hot rod. Rothsport is of the same thought the velocity of the standard head works better.
Last edited by schmidtwerk; 01-03-2016 at 03:35 AM.
Reason: Misspell
Outstanding. What exhaust and cats were on the car at testing? Stock airfilter? Anything else not stock but programming?
Stock cats, silencers, air filter and air box. Ran up on fresh 97 Octane (RON) UK fuel and remapped only. 320hp is about as good as it gets through stock cats in my experience.
Agree and have seen zero gain from RS heads. Rothsport build and dyno' approx 10 3.8 VRAM motors with RS cams. All had Giac or Wong chips, similar exhaust. The engine run on their in house engine dyno. Two real M64/20 motors were run, mine from a 993RS made 301hp with full stock including exhaust. Another had programming and the typical hot rod exhaust for use in early cars made just shy of 310hp. The balance of the engines used stock heads but with RS valves....all as strong or stronger than the RS head motors. The strongest was 324hp another of mine in an early hot rod. Rothsport is of the same thought the velocity of the standard head works better.
Glad that we're all singing the same tune (pun intended), apart from Porsche that is. The engineers approach to cylinder head design is to consider discharge coefficient rather than flow (DC being the relation between flow rate per unit area, e.g. cfm/sq.in.), match the port flow to the engine air flow demand and combine the camshaft lift with the DC to match that demand over the intake cycle. Doing this will result in looking for a smaller port head. The 964 head is a better starting point than the 993, however it is a pain to fit to the 993 due to having only one pair of exhaust studs which is why (some 10 years ago) we embarked on manufacturing the 9m billet heads.
The 9m head uses 993 50mm/42.5mm valves with smaller, high velocity ports on the intake and exhaust. As an aside we did calculate that we could have used a smaller exhaust valve than the 993 size, in the end deciding to optimise around stock to allow the use of standard valves.
Stock cats, silencers, air filter and air box. Ran up on fresh 97 Octane (RON) UK fuel and remapped only. 320hp is about as good as it gets through stock cats in my experience.
Based on what I've seen on the Rothsport dyno 320hp for stock but with programming is really good. Those figures usually only reserved for cars running an unrestrictive exhaust. Is this programming that you used on this other X51 something you sell?
Based on what I've seen on the Rothsport dyno 320hp for stock but with programming is really good. Those figures usually only reserved for cars running an unrestrictive exhaust. Is this programming that you used on this other X51 something you sell?
We can replicate the program on any 55 pin ROW ODB1 ecu.
The 88 pin US OBD2 version is a whole new ballgame....
Looked at a chart and thought 97RON was equal to about 92 Yankee rating?
Fair point, my bad. We tune all our cars on Shell V-Power which is rated at 97 but actually more like 98/99, hence around 93/94 in US terms. For UK Rennlisters the other good alternative is Tesco 99.
Colin,
Sent you an email. Our mutual buddy was kind enough to make the intro. Here is what the back of the ECU looks like on a factory X51....clearly shows "993RS".
Last edited by schmidtwerk; 01-07-2016 at 01:36 PM.
Reason: Mis spell
Geo, Thnks for posting it. What are "TU's" on the last page? Tributary Units? How does it relates to time? Interesting to see what amount of labor Porsche estimated for this.
TU = Time Units, Porsche speak for 1/100 of an hour, the minimum bookable time at Porsche workshop labour rates. Apparently decimal hours are much more expensive than normal hours, a fact you can confirm with a visit to any OPC service centre.
Rothsport just finished dyno run. 308hp 281 torque. Made 285hp initially AFTER the cam timing was correctly reset from .6mm to 1.8mm, a torn boot at the intake runner to injector stack was replaced, new caps, rotors, plugs, wires and injectors cleaned and tested. Then once on the dyno an internal leaking solenoid prevented one intake runner from operating and the other partially operating. Once corrected made 308hp. Looks like before any work was done it would have struggled to make 275hp.
01-02-2016, 06:46 PM
