http://www.speedoptions.com/articles/2327/then"Equation 2 basically shows that if the lift is greater than ¼ valve diameter, you are wasting your time. It is possible to go a little higher (say 0.3L/D or even upto 0.33L/D, depending on port geometary) since the valve stem and other flow reducing compoenents need to be factored in. HOwever, in these cases larger valves are usually needed. "http://staffi.lboro.ac.uk/~elvpc/papers/VL.htm
so 1.5" x0.25=0.375" however the Q has a 0.390" peak liftso 1.5" x0.30=0.450"...........so 9.9 mm vs 11.43mm ideal
http://www.qnet-cfd.net/newsle...4.pdf
thenhttp://www.eng.fsu.edu/~shih/e...s.pdf
now some homework:http://www.eng.fsu.edu/~shih/e...s.pdfh ... wertrains/
http://www.gmrc.org/gmrc/techpaperspdf/AirFlow.pdf
So much info so easy to find just search on google "engine valve curtain area" and " valve curtain area"
Valves
I had some custom cams welded up for a previous 4 cam V-8 (Porsche 928) increasing the lift and duration. I installed them and then drove 1000 miles before having the ECU optimized for the cams. I was surprised that most of the performance increase was from the cam change, prior to the reprogramming. Would the Q45 ECU adapt to a cam change that effectively?
-
Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Except for the lift as the valves get very close when the rods stretch at high rpms...........but you could probably deepen the fly cuts on pistons by 0.5 mm.There is some reserve range in the ecu as the MAF never gets above 4.44 volts. 5.0 volts would be 255 grams per second [something close to 375 HP]...........the exhaust cam duration [248] and closing point [8 DegATDC] is the factor that sets the rpm where the HP peaks [and conversely where the torque peaks [4,000 rpm]]........another 10 degrees on exhaust cam split 50/50 would raise the rpm to 6600 but you would need to retune the runner length to meet the new rpm.
If emissions nor idle smothness were a concern 360-370 HP at 6600 rpm would be easily safe and possible...........but the cost for cams and piston work and casting a new shorter plenum by 1.0"...............makes a little light duty supercharging look cheap.
The JWT ecued torque [337 lb/ft is limited by the VE].......tuliping the intake valves maybe a little more duration....might net 8-10 more lb/ft at 4750 rpm.
They redesigned the whole engine and ended up with 340 HP and 333 lb/ft but they had to meet stiffer emissions.
Just not cost effective.........simplest thing to do would be to remove plenum and have 8 tuned stacks with TB each and a massive computer to guess at air flow or just measure it at one {karmen vortex type}. Then actually use exhaust gas temperature and an O2 on each exhaust port pipe to set mixture like they do in formula one.
Too ragged edge for me.
928 were fun had one in 1985, my friend in Puerto Rico has 3.Used to be in the same industrial complex in FLA with a shop that built racing Porsche got to drive everything.
The Q ecu does not adapt very much to WOT, only part throttle....there is a little trim from the MAF but mostly protective [heat] as JWT has to lean 10% for the power increase and increase timing progressively by 3 deg.
If emissions nor idle smothness were a concern 360-370 HP at 6600 rpm would be easily safe and possible...........but the cost for cams and piston work and casting a new shorter plenum by 1.0"...............makes a little light duty supercharging look cheap.
The JWT ecued torque [337 lb/ft is limited by the VE].......tuliping the intake valves maybe a little more duration....might net 8-10 more lb/ft at 4750 rpm.
They redesigned the whole engine and ended up with 340 HP and 333 lb/ft but they had to meet stiffer emissions.
Just not cost effective.........simplest thing to do would be to remove plenum and have 8 tuned stacks with TB each and a massive computer to guess at air flow or just measure it at one {karmen vortex type}. Then actually use exhaust gas temperature and an O2 on each exhaust port pipe to set mixture like they do in formula one.
Too ragged edge for me.
928 were fun had one in 1985, my friend in Puerto Rico has 3.Used to be in the same industrial complex in FLA with a shop that built racing Porsche got to drive everything.
The Q ecu does not adapt very much to WOT, only part throttle....there is a little trim from the MAF but mostly protective [heat] as JWT has to lean 10% for the power increase and increase timing progressively by 3 deg.
-
Mayhem_J30
- Posts: 2643
- Joined: Tue Apr 30, 2002 2:00 am
- Car: Ummm...My Car
- Location: Louisville, KY
so much information, this reminded me of a joke
Jason Mgin walkes up to his teacher at the end of his physics exam, and hands in his exam, and has a few final words to say.
" Mr.Peddle, i just want you to know that i studied really hard for this exam, i read the book over and over, made lots of notes, and finaly condensed it into 32 pages"
Mr.Peddle looks at Jason in amazement, Jason wasnt one to actualy study hard for anything in his view " wow jason, thats great, i hope you did well on your exam, and i would like to see those pages, i want to see how you managed to condense it like that"
Jason replies " sir, but thats not it, i decided that it wasnt enough, so i thought about it for along time, went over the notes and the book again, and finaly condensed all the material into 2 pages!"
" wow, that incredible, i never expected this much from you"
" yes but not done yet! i still wasnt satisfied, and i crammed all night and finaly condensed the entire course material into TWO WORDS!!"
At this Mr.peddle raised his eye brows in amazement, how can this kid condense the entire 1000 page physics book into 2 simple words? " so what are the two words Jason?"
BULL ****
i realize more and more from reading such knowledge filled sites that modding cars isnt about sticking turbo's on and writing mugen all over you car. Thanks Q45 you just enlightned one more person. Now i just need to read it over and over again... lol
Jason Mgin walkes up to his teacher at the end of his physics exam, and hands in his exam, and has a few final words to say.
" Mr.Peddle, i just want you to know that i studied really hard for this exam, i read the book over and over, made lots of notes, and finaly condensed it into 32 pages"
Mr.Peddle looks at Jason in amazement, Jason wasnt one to actualy study hard for anything in his view " wow jason, thats great, i hope you did well on your exam, and i would like to see those pages, i want to see how you managed to condense it like that"
Jason replies " sir, but thats not it, i decided that it wasnt enough, so i thought about it for along time, went over the notes and the book again, and finaly condensed all the material into 2 pages!"
" wow, that incredible, i never expected this much from you"
" yes but not done yet! i still wasnt satisfied, and i crammed all night and finaly condensed the entire course material into TWO WORDS!!"
At this Mr.peddle raised his eye brows in amazement, how can this kid condense the entire 1000 page physics book into 2 simple words? " so what are the two words Jason?"
BULL ****
i realize more and more from reading such knowledge filled sites that modding cars isnt about sticking turbo's on and writing mugen all over you car. Thanks Q45 you just enlightned one more person. Now i just need to read it over and over again... lol
Q45tech wrote:Just remember you can't have it both ways, or couldn't until recently: variable continuous cam advance and variable plenum and runner length............now all we need to add is variable lift [not steps like Honda] and direct injection -- all simultaneously!
... and we can do away with throttle bodies. I see where you're going!!!! You want to put hundreds of honest guys who make throttle bodies out of business! All in the name of fuel effiency and "progress"!