+1 on the EGT's especially the 93.

 

Smoken , crazy power on pump , insanse street car.

 

The car does not have an EGT gauge, so stop asking

 

LOL, Thanks Dave. I was curious only because I have always found it elusive on how to achieve a high boost, pump gas set-up, (93 Oct. in my case) without the high EGT's. It seems inevitable on the long 5th gear pulls.

 

Somethting im always thinking about, is the difference in porting a n/a head versus a turbo head. On a turbo car I tend to think of the exhaust ports/manifold the same as the intake. Meaning your feeding the turbo much the same as an intake is feeding the cylinders.

Going big in the x ports (anything particularly larger than the cross sectional area beind the valves) could potentially do nothing but slow velocity down, which should hurt spool. However in keeping the thinking consistent and viewing the exhaust of a turbo engine similar as an intake on any engine... You could also argue that enlarging the ports before they all funnel back down into the turbo could act as a plenum, and could be useful in certain points of the rpm range.

With out testing, my theory on mitsu heads (dsm at least) is concentrate on bowl, short turn radius, and dividers in the exhaust. (If you have the guides out anyway, maybe in that area). I have seen people knife edge intake dividers. On top of not going along with the tear drop theory, I would hate to mess with the area injectors are aimed at...

Another thing I day dream about is on a turbo engine how different ports affect the actual air the cylinder sees. To be more specific, say you have indentical setups with acception of cylinder heads. Both running the same boost, measured @ the intake manifold, only one has large ports. What is the difference in cylinder pressure between the two? Flow Vs. Pressure disscussion... I think people were trying to make the connection between ported heads and running higher boost at lower octane and or more timing, but you would think better ports would increase cylinder pressure @ the same boost, making it more prone to det?

I had heard the Ecotecs have tiny ports. Last fall at the Nopi finals in Norwalk there was an ecotec powered dragster there. I think it was running low 7s or so probably high 7 second if in a tube frame fwd. At any rate he had the manifolds off, and the ports in deed looked tiny compared to dsm/evo ports. It just kind of makes you think.


Sorry for the rambling on your thread Dave.

 

i think it says it pretty clearly in buschur's signature,,

"ONCE AGAIN HOLDER OF FASTEST MPH, 172.74."

 

But there is a substantial difference in gas temperature between the two, and as you know, temperature is a critical variable in gas law. This is why equal flow (as measured on a flow bench) between int and exh ports does not constitute 'balance'.


That would only serve to reduce exhaust gas velocity and pulse energy. The function of a plenum only serves the intake side.


The answer will vary with RPM and VE characteristics, assuming of course all else is equal. All things considered, the smallest port that does the job without choking is best.


All else being equal, improving intake flow while relieving exhaust pressure/reversion at the same time reduces combustion charge temps, which reduces the detonation threshold - all at the same indicated manifold pressure. This illustrates why intake manifold pressure alone is of limited value without knowing exh manifold pressure.


Sorry to sidetrack . . .

 

Buschur does it again! These guys keep getting better and better. I think the cold climate must have a mind enhancing effect. Either that or they are taking Nootropics 24/7. http://en.wikipedia.org/wiki/Nootropic

TedB needs to change his User Name to Wkd-Smrt-Ted for being the ultimate brainiac!

 

Sorry if I missed it, but was this the tubular or cast manifold?

 

LOL

I've dabbled in my fair share of acetyl-L-carnitine, aniracetam, DMAE, and phosphatidylserine, but you have to be very careful with these. If miused, some of them can put more hurt on you than a 42R on a stock block.

 

 

Not to turn this into a geek festival... but I must elaborate. Temperature is the reason, true, but the explanation is due to the increase in mach number.

Higher temperatures raise the local mach number significantly. So, the sonic limit before choking is much, much higher. A given port can flow a whole lot more when the working fluid is hot, and this is why exh ports (and exh valve lift and size) can be smaller than on the intake side.

 

Good stuff. A few of the things I was actually just playing devils advocate against my own theories.

I actually never thought about temperature differences. On top of that it has been a decade since I studied any of that since I never finished my engineering degree, and pursued engine machining/building. Im not exactly sure where the equal flow v. balance fits in to my rambling. I understand there will be less exiting than entering the cylinders even with heat expansion?

I agree. Thats one of the things I was playing devils advocate against myself. As stated above my theory is going big on the x ports is just reducing velocity.



I guess thats another balance issue. Keeping reversion/ex pressure down while keeping velocity up.

All things I think about all the time, its just not the easiest thing to test. Good flow bench numbers wouldnt necessarily tell you the best port for different turbo setups.

 

I can assure you guys I don't have any freaking clue what you are all talking about

I can also assure you that when Marque picked up his car today and him and I went for a test drive the smile on his face was priceless and looked like he had been sniffing some nitrous gas! He was very happy with the car, especially when it turned sideways in the road in 2nd gear. I love seeing that look on a guys face.

Hopefully he will be making post here about the car and his experience. He's on his way back home driving it straight through to Virginia.

Hope you had a great drive back Marque.

 

"Sideways in second gear" should be a song - looking forward to reading Marque's post!