4.1 Flat 6 Innovations 964 Build Up Pictorial
02-14-2016, 09:18 AM
#76
Jake, thanks indeed for spending the time to write a response.
I) To start with your comments on reading dyno sheets: Indeed many people in general are unaware of HP being a derivative of torque, the equation of which leading to the lines to cross at 5252RPM -when displaying Torque lbs.ft. rather than Nm- . Indeed many of those only focusing on max HP without fully understanding what the rest of the graph is about. A fact shown by those attending your hi performance class.
This being representative for the entire Rennlist community is a bit of a misguided assumption however, and that's not opinion...it's fact. Just have a look at some of the in depth technical discussions on the 964 board concerning dyno sheets and underlying: BMEP, CR associated effects on timing and cylinder head temps, the effects of port velocity vs. outright flow, cam lift and timing, varioram vs. short stack ITB's etc. This goes well beyond the basic ability of having an intelligent conversation following the posting of a dyno sheet, with many of the less initiated learning in the process me included.
But maybe that's the reason for people attending your classes in the first place...not having too much knowledge on the subject to begin with coupled to the willingness to learn? As stated this is not fully representative of the community here....whether or not you want to fuel any debate / learnings on here by posting dyno sheets and associated comments is of course entirely up to you.
II) To follow with your comments on anyone being able to produce ridiculous peak power: Of course there's some truth in your bigger is better comments "a lot of cam, a lot of port, a lot of compression, a lot of intake, a lot of exhaust" . However, what the above also needs is a lot of revs to produce the power, as well as mechanical and thermal stability to make the engine last....both of which are not so easy on our aircooled engines which at standard are safe to about 6900RPM and don't like much more than 11,5:1 static CR when running cams that have max power below 7500RPM.
So yes, with lots of money thrown at cranks, rods, cylinders, valve gear, intake and exhaust one could produce a high peak HP engine that lasts. Whether or not it produces any goods below peak power is up to the thought and engineering that goes into it....I see some distinct parallels with you building a 37K motor here ;-)
III) Your comment on tuners and Honda's: A game of semantics; om verdere misverstanden te voorkomen zal ik me in het Nederlands uitdrukken. In Europa is het woord tuner gerelateerd aan de race industrie, denk aan RS-tuning / Reinhold Schmirler die internationaal zijn sporen heeft verdiend in Porsche racerij. I'm talking about our engines here, being 3.6-3.8 liter two valve air cooled engines that produce about 270HP-340HP in factory Cup form (the latter being 993 Cup). With the likes of Ninemeister, Cosworth and Robert Linton/Weissach amongst a select few others developing these into streetable 380HP+ engines.
IV) Equal length headers producing peak torque over a limited rev range being my perception / if not opinion.: This is not opinion.....it is science!
As soon as the exhaust valve opens a pressure wave moves down the primary, whenever this pressure wave encounters a positive change in cross sectional area (i.e. a larger pipe, collector, atmosphere) a reflected inverted pressure wave is generated. If the negative pressure wave can be arranged to arrive back at the exhaust valve during valve overlap, fresh mixture can be sucked into the cylinder to the amount sometimes called the 5th cycle in a four stroke engine.
Now the big word here is if. The timing at which the negative wave is reflected back depends on the time at which the positive wave generated during initial exhaust valve opening (speed of sound within the gas temperature vs. primary length) reaches the collector to be reflected back. This timing being beneficial or not depends entirely on the RPM the engine is operating at -or time frame at which the engine rotates a given amount of degrees towards exhaust stroke valve overlap- Being revved to slow has reflected waves arriving too early and vice versa.
When building equal length headers one needs to know what length is needed to be beneficial at which revs to begin with! This introduces a peak at that rev range, using unequal length headers spreads this range of benefit per individual cylinder. Again not perception....just physics.
Of course, getting the most out of an engine requires focusing on the entire chain as you rightly state. The induction efficiency is partly responsible for the exhaust pressure wave intensity to begin with, as is ignition timing....the latter also being responsible for EGT's and speed of sound acordingly. Cam timing the same...the question is am I timing my exhaust to my cam or the other way around? Complicated stuff in all, with many F1 teams using advanced simulation and CFD modelling techniques to get the most useable power. Those using controlled dyno development for street/competition applications can achieve very good results indeed....simply throwing some stuff together hardly ever will.
Good luck with building your 4.1 , I think there are some interesting details in there compared to other builds listed on here....I look forward to seeing the dyno results should you ever decide to post them on here :-)
Cheers,
H
I) To start with your comments on reading dyno sheets: Indeed many people in general are unaware of HP being a derivative of torque, the equation of which leading to the lines to cross at 5252RPM -when displaying Torque lbs.ft. rather than Nm- . Indeed many of those only focusing on max HP without fully understanding what the rest of the graph is about. A fact shown by those attending your hi performance class.
This being representative for the entire Rennlist community is a bit of a misguided assumption however, and that's not opinion...it's fact. Just have a look at some of the in depth technical discussions on the 964 board concerning dyno sheets and underlying: BMEP, CR associated effects on timing and cylinder head temps, the effects of port velocity vs. outright flow, cam lift and timing, varioram vs. short stack ITB's etc. This goes well beyond the basic ability of having an intelligent conversation following the posting of a dyno sheet, with many of the less initiated learning in the process me included.
But maybe that's the reason for people attending your classes in the first place...not having too much knowledge on the subject to begin with coupled to the willingness to learn? As stated this is not fully representative of the community here....whether or not you want to fuel any debate / learnings on here by posting dyno sheets and associated comments is of course entirely up to you.
II) To follow with your comments on anyone being able to produce ridiculous peak power: Of course there's some truth in your bigger is better comments "a lot of cam, a lot of port, a lot of compression, a lot of intake, a lot of exhaust" . However, what the above also needs is a lot of revs to produce the power, as well as mechanical and thermal stability to make the engine last....both of which are not so easy on our aircooled engines which at standard are safe to about 6900RPM and don't like much more than 11,5:1 static CR when running cams that have max power below 7500RPM.
So yes, with lots of money thrown at cranks, rods, cylinders, valve gear, intake and exhaust one could produce a high peak HP engine that lasts. Whether or not it produces any goods below peak power is up to the thought and engineering that goes into it....I see some distinct parallels with you building a 37K motor here ;-)
III) Your comment on tuners and Honda's: A game of semantics; om verdere misverstanden te voorkomen zal ik me in het Nederlands uitdrukken. In Europa is het woord tuner gerelateerd aan de race industrie, denk aan RS-tuning / Reinhold Schmirler die internationaal zijn sporen heeft verdiend in Porsche racerij. I'm talking about our engines here, being 3.6-3.8 liter two valve air cooled engines that produce about 270HP-340HP in factory Cup form (the latter being 993 Cup). With the likes of Ninemeister, Cosworth and Robert Linton/Weissach amongst a select few others developing these into streetable 380HP+ engines.
IV) Equal length headers producing peak torque over a limited rev range being my perception / if not opinion.: This is not opinion.....it is science!
As soon as the exhaust valve opens a pressure wave moves down the primary, whenever this pressure wave encounters a positive change in cross sectional area (i.e. a larger pipe, collector, atmosphere) a reflected inverted pressure wave is generated. If the negative pressure wave can be arranged to arrive back at the exhaust valve during valve overlap, fresh mixture can be sucked into the cylinder to the amount sometimes called the 5th cycle in a four stroke engine.
Now the big word here is if. The timing at which the negative wave is reflected back depends on the time at which the positive wave generated during initial exhaust valve opening (speed of sound within the gas temperature vs. primary length) reaches the collector to be reflected back. This timing being beneficial or not depends entirely on the RPM the engine is operating at -or time frame at which the engine rotates a given amount of degrees towards exhaust stroke valve overlap- Being revved to slow has reflected waves arriving too early and vice versa.
When building equal length headers one needs to know what length is needed to be beneficial at which revs to begin with! This introduces a peak at that rev range, using unequal length headers spreads this range of benefit per individual cylinder. Again not perception....just physics.
Of course, getting the most out of an engine requires focusing on the entire chain as you rightly state. The induction efficiency is partly responsible for the exhaust pressure wave intensity to begin with, as is ignition timing....the latter also being responsible for EGT's and speed of sound acordingly. Cam timing the same...the question is am I timing my exhaust to my cam or the other way around? Complicated stuff in all, with many F1 teams using advanced simulation and CFD modelling techniques to get the most useable power. Those using controlled dyno development for street/competition applications can achieve very good results indeed....simply throwing some stuff together hardly ever will.
Good luck with building your 4.1 , I think there are some interesting details in there compared to other builds listed on here....I look forward to seeing the dyno results should you ever decide to post them on here :-)
Cheers,
H
Last edited by evoderby; 02-14-2016 at 05:18 PM.
06-17-2018, 05:39 AM
#77
Haven’t been on Rennlist much lately but -in light of the discussion in this very thread- found this an interesting post in Robert Linton’s thread:
https://rennlist.com/forums/964-foru...l#post15059221
The author ‘Race developments’ who in the thread you’re now reading was introduced as the OP’s (Flat6) exhaust supplier is stating the following:
“When I was doing my extensive exhaust development on the M64 engine, I never achieved the best results with equal length headers in regards to horsepower. Equal length gave a small percentage bump in torque between 4-4400rpm, but lost hp above 6000. I always achieved the best torque curve with 2 long primaries, 2 mid length, and 2 short.”
Elephants & memory and all that.... ;-)
https://rennlist.com/forums/964-foru...l#post15059221
The author ‘Race developments’ who in the thread you’re now reading was introduced as the OP’s (Flat6) exhaust supplier is stating the following:
“When I was doing my extensive exhaust development on the M64 engine, I never achieved the best results with equal length headers in regards to horsepower. Equal length gave a small percentage bump in torque between 4-4400rpm, but lost hp above 6000. I always achieved the best torque curve with 2 long primaries, 2 mid length, and 2 short.”
Elephants & memory and all that.... ;-)
10-31-2018, 08:11 PM
#78
Haven’t been on Rennlist much lately but -in light of the discussion in this very thread- found this an interesting post in Robert Linton’s thread:
https://rennlist.com/forums/964-foru...l#post15059221
The author ‘Race developments’ who in the thread you’re now reading was introduced as the OP’s (Flat6) exhaust supplier is stating the following:
“When I was doing my extensive exhaust development on the M64 engine, I never achieved the best results with equal length headers in regards to horsepower. Equal length gave a small percentage bump in torque between 4-4400rpm, but lost hp above 6000. I always achieved the best torque curve with 2 long primaries, 2 mid length, and 2 short.”
Elephants & memory and all that.... ;-)
https://rennlist.com/forums/964-foru...l#post15059221
The author ‘Race developments’ who in the thread you’re now reading was introduced as the OP’s (Flat6) exhaust supplier is stating the following:
“When I was doing my extensive exhaust development on the M64 engine, I never achieved the best results with equal length headers in regards to horsepower. Equal length gave a small percentage bump in torque between 4-4400rpm, but lost hp above 6000. I always achieved the best torque curve with 2 long primaries, 2 mid length, and 2 short.”
Elephants & memory and all that.... ;-)
good stuff. thanks for circling back.
dumb question: do fuel and timing need to be trimmed per cylinder for unequal length headers?
11-02-2018, 12:39 PM
#79
There are pictures of cylinders going on this engine 3 years ago. The build got stalled due to a valve manufacturer? Curious to see the outcome/completion - but man....3 years.
11-02-2018, 08:21 PM
#80
Technical Guru
Rennlist Member
Rennlist Member
11-02-2018, 08:47 PM
#81
Rennlist Member
04-17-2019, 07:54 AM
#83
Former Vendor
Thread Starter
