3.8 Upgrade?
03-22-2014, 03:36 PM
#62
I'm hoping that this dyno curve will be an encouragement to your 4.0 project. This is the performance of a 9m built 3.82 litre Singer engine on 9m ITB intake compared to a stock 996GT3RS with its factory twin plenum intake. I'm not sure I see an advantage of using the GT3 intake - maybe I'm missing something? 
03-22-2014, 04:00 PM
#63
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Talk about pot half empty......?
All intake systems have a tuned (resonant) length which is dependent on the diameter, length and volume of the whole intake port & runner - i.e. the cylinder head, manifold, throttle body (if individual) & bellmouth (for ITB) or head, injector stack and runner (for plenum). Those dips in the torque curve that you are looking at are simply points of low VE (volumetric efficiency) which lie in between the harmonic tuned lengths of the runners. Most intake systems peak tune on the 3rd harmonic and have minor peaks on the 4th and 5th harmonics, hence the dip you mention on the 9m engine at 4700rpm is the gap between the 5th and 4th harmonics. Ironically I found it more intriguing that the GT3 intake had larger dips at 4000rpm & 5500rpm between 5th/4th & 4th/3rd harmonics than the 9m ITB system, pointing to the GT3 system relying on resonance for its VE whereas the 9m system relies more on a higher intake velocity and thus being less sensitive to the harmonic tuning.
Interestingly the first time I ever had a drive of a GT3 the first thing I noticed were the peaks and troughs in the torque curve going through the full rpm range at full throttle, whereas I never felt that with the 3.8 engine in my 993RS-R.
Of course, the next stage for 9m is to redesign the whole intake runner to achieve a still higher velocity with strong resonant tuning.....
All intake systems have a tuned (resonant) length which is dependent on the diameter, length and volume of the whole intake port & runner - i.e. the cylinder head, manifold, throttle body (if individual) & bellmouth (for ITB) or head, injector stack and runner (for plenum). Those dips in the torque curve that you are looking at are simply points of low VE (volumetric efficiency) which lie in between the harmonic tuned lengths of the runners. Most intake systems peak tune on the 3rd harmonic and have minor peaks on the 4th and 5th harmonics, hence the dip you mention on the 9m engine at 4700rpm is the gap between the 5th and 4th harmonics. Ironically I found it more intriguing that the GT3 intake had larger dips at 4000rpm & 5500rpm between 5th/4th & 4th/3rd harmonics than the 9m ITB system, pointing to the GT3 system relying on resonance for its VE whereas the 9m system relies more on a higher intake velocity and thus being less sensitive to the harmonic tuning.
Interestingly the first time I ever had a drive of a GT3 the first thing I noticed were the peaks and troughs in the torque curve going through the full rpm range at full throttle, whereas I never felt that with the 3.8 engine in my 993RS-R.
Of course, the next stage for 9m is to redesign the whole intake runner to achieve a still higher velocity with strong resonant tuning.....
There are many ways of going about intakes on these cars, wanting to learn, and to actually understand the why behind it.
Your information is much appreciated. Also intrigued at how you are going to manage velocity and resonance, will be very interesting.
03-22-2014, 06:38 PM
#64
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Colin very well designed engineered Porsche engines and components. I would like to have 400 HP on a mixture of pump gas and racing fuel . On my engine what would I need to replace to get there. I am assuming replacing the entire plastic penguins and mad and swapping in your system and appropriate ecu
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03-23-2014, 04:33 PM
#65
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Colin very well designed engineered Porsche engines and components. I would like to have 400 HP on a mixture of pump gas and racing fuel . On my engine what would I need to replace to get there. I am assuming replacing the entire plastic penguins and mad and swapping in your system and appropriate ecu
The keyword to any successful engine build is synergy, Joe; the mixing and matching components is not the way forward unless you want to carry out your own 10,000 hour engine development program. The engines from the graphs above were run on UK 97 octane pump gas and I would say were pretty much as close to the limit that you could achieve with conventional tuning methods.
The specification of the 425hp 3.82 litre reads something like:
Stock 993 crank (with 7700rpm limit) or GT3 crank (8000+ limit)
9m 132mm centres conrods (or equivalent)
9m 103 pistons & cylinders
9m billet heads
9m Valves, spring kit, Ti retainers
9m Race cams (13mm lift)
9m billet rockers
9m ITB intake system
9m equal length header system (1.75", Burns collectors)
Motec M800 engine management, 9m wiring harness
03-23-2014, 04:42 PM
#66
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I should also mention that we due to air flow installation on the 9m dyno being specifically designed for air cooled 911 engine testing and mapping we usually see slightly more power when compared to other dyno installations. I see that as an engineering problem that the others need to address, not 9m.
Last edited by NineMeister; 03-23-2014 at 06:52 PM.
03-23-2014, 06:32 PM
#67
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So it would be a reasonable assumption that any of the horsepower or torque figures that 9m cites from their specially set up engine dyno are in the neighborhood of 12.6% greater relative to typical or officially published results for an identical engine ((1 - 284/325) x 100). I'm not sure if this correction factor would scale consistently or not across the whole RPM range, but it is still good to know that not all engine dynos yield comparable results and is certainly worth keeping in mind when comparing data between performance shops.
Kudos to 9m for including known reference engines in their charts. Very good to know!
Kudos to 9m for including known reference engines in their charts. Very good to know!
03-23-2014, 06:41 PM
#68
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One should be very careful comparing hp data from shop to shop.
As Colin mentions, dynos are tuning devices used for internal comparative data and are not the precise instrument we would all love to have to match engine builders.
There are precious few great air cooled shops on either side of the pond; if I lived and raced over on his side, Colin would certainly have my work. Here, I truck my cars halfway across the country to get to my guys.
I'll edit to add, at the Club race level, 25hp one way or the other means nothing as the driver is by far the greatest single variable.
As Colin mentions, dynos are tuning devices used for internal comparative data and are not the precise instrument we would all love to have to match engine builders.
There are precious few great air cooled shops on either side of the pond; if I lived and raced over on his side, Colin would certainly have my work. Here, I truck my cars halfway across the country to get to my guys.
I'll edit to add, at the Club race level, 25hp one way or the other means nothing as the driver is by far the greatest single variable.
03-23-2014, 07:04 PM
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So it would be a reasonable assumption that any of the horsepower or torque figures that 9m cites from their specially set up engine dyno are in the neighborhood of 12.6% greater relative to typical or officially published results for an identical engine ((1 - 284/325) x 100).
03-23-2014, 09:57 PM
#71
It's a good point which is down to the calculation software of the Dynostar system and one which I have never really been bothered enough to address. All I can tell you is that the hp numbers that the 9m dyno measures has been compared to engine dyno & other chassis dyno results for the same engine are within less than 1% error, which is more than good enough to me. Putting it simply any chassis dyno is a comparative tool, hence I always focus on the differences in the shape of the power curves rather than getting hung up over the absolute numbers. That's why on these plots I'm comparing a championship winning 993RS engine with a known performance yardstick - the 996GT3RS - tested under the same test conditions.
Here's a plot from Fabspeed showing 6GT3 baseline vs the EVOMSit reflash they offer. Joe, is this typical of the various stock-ish GT3's you've tested?
03-24-2014, 01:02 AM
#72
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But the engines weren't tested under the same conditions - the 9M run shows a temperature of 8.3C (47F!) while the GT3 was run @ 29C (85F). Accounting for that, the only reasonable conclusion is that the 3.82L makes about the same power & TQ as a 6GT3 - ~385hp / 284ft*lbs. Still impressive, but not quite 425/325.. would be good to sort out the calculations made by the dyno software.
Interesting
03-24-2014, 01:08 AM
#73
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But the engines weren't tested under the same conditions - the 9M run shows a temperature of 8.3C (47F!) while the GT3 was run @ 29C (85F). Accounting for that, the only reasonable conclusion is that the 3.82L makes about the same power & TQ as a 6GT3 - ~385hp / 284ft*lbs. Still impressive, but not quite 425/325.. would be good to sort out the calculations made by the dyno software. Here's a plot from Fabspeed showing 6GT3 baseline vs the EVOMSit reflash they offer. Joe, is this typical of the various stock-ish GT3's you've tested?
03-24-2014, 06:22 AM
#74
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03-24-2014, 08:56 AM
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