BuckeyeSVT Posted October 4, 2007 Author Share Posted October 4, 2007 Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 ..Dom,send me the cam 'selection' you have and I will set up and measure them etc.... Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 I observe that the old 'bigger is better' card is being played again on intake ports, oval Vs twin in port area.Area is only part of the design issue.Larger ports before the intake throat(in the head)as it reaches 'Zone 2 (the area just behind the valve seat in the port that has a venturi)...all this does is slow the incoming charge.Firms like Dart have shown on wet flow testing, that hogging out ports does not add HP,in fact they state that to keep ports at design size is usually better for HP.If you go crazy and hog out heads aswell all you do is slow it even more.Same old story here,no one seems to understand the need for high gas velocity,all I ever hear is CFM...which is only part of the calc...This bigger is better is still a hangover from the 2 valve pushrood days...Maybe we need our 'super motor' with 3 inch intake valves and a 2 inch valve lift to proove the the point that if you kill velocity you kill HP and all you do is push the peak HP range higher up the rev band waiting for the gas velocity to 'catch up'...it's all in the math guys!! ;) Link to comment Share on other sites More sharing options...
Guest D's nuts Posted October 4, 2007 Share Posted October 4, 2007 THen why do all these race drag cars have hoged out head ect and and have like 2k hp or w/e? I t must be needed at some point. SO how do you know when that is? Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 ...not many DOHC drag cars!...Maybe the Prodrive Aston-Martin race team have got it all wrong eh!!! Link to comment Share on other sites More sharing options...
BuckeyeSVT Posted October 4, 2007 Author Share Posted October 4, 2007 THen why do all these race drag cars have hoged out head ect and and have like 2k hp or w/e? I t must be needed at some point. SO how do you know when that is? NASCAR... old technology (not anymore.. however). Overhead valve engines with cam in block (2 valves per cylinder). Compare an apple to a watermelon - OHV engine vs DOHC (Double Over Head Camshaft). Two entirely different technologies and they work on different principles. No NASCAR engine has 4 valves per cylinder. Period. What's good for one is not good for "all". -Dom Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 ...fire up the John Deere Dom...we are back in time again!!!I'll dig out the specs of the Prodrive Le Mans Aston-Martin V12 engine,must be wrong...as they won!!! Link to comment Share on other sites More sharing options...
Guest D's nuts Posted October 4, 2007 Share Posted October 4, 2007 No need to be a smart ass. I was asking a question. I didnt say everything applied to a DOHC ( Double Over HEad Cam) THats why I asked " why " Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 No need to be a smart ass....Nice,thanks! Link to comment Share on other sites More sharing options...
BuckeyeSVT Posted October 4, 2007 Author Share Posted October 4, 2007 No need to be a smart ass. I was asking a question. I didnt say everything applied to a DOHC ( Double Over HEad Cam) THats why I asked " why " Lol... I am a "smart ass", ask anyone who knows me. The bigger is better theory works on "iron" OHV engines. Back in the day (60's-80's) most engines were built from the factory restricted. Sure, porting and polishing and adding bigger valves was the answer - today that is not the case. What's the point of explaining all this - Terry has pointed it out over the years here... And I've chimed in numerous times. Bigger isn't better on OHC engines. We have no PI heads for Contours and even the PI heads for the 4.6L weren't PnP with bigger valves. Velocity and port speed is a bigger factor than port flow and port size. I guess if I get six 3" pipes with throttle plates for each cylinder that will make the most power... Hey - Why didn't I think of that before.. 2 triple stacks out of my hood!! Because, these are street cars - Not race cars. Perhaps if everyone was interested in "all ranges" and not fixated on "Highest Power" from 5300-6750 this discussion would be more relevant. I guess more midrange punch from a straight 3L is pointless... Perhaps a graph may show this in better light (In SAE of course, wouldn't want another monkey on my back). I'm not biased remember, I'm not selling a product here...lol. -Dom Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 Dom,do me a favor and get up to date! The Le Mans (winning)Prodrive V12 Aston makes its max power at 5750 RPM,redline at 6750 RPM and runs restrictor plates...so where is all this high RPM power bunk eh.?..Get with the times Dom..!!! Link to comment Share on other sites More sharing options...
Guest D's nuts Posted October 4, 2007 Share Posted October 4, 2007 Well obviously theres a point when to big is to big. I was talking about something mild but TOM I mean DOM thank you for pointing that out for me hehe Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 FWIW the A-M V12 also runs 2(one per bank) restrictor plates of 30.7 MM each...now tell me again about bigger t/bodies and such!!!(thats a 3.0 running with one 30.7 MM plate!)...so with these in place how do we make power huh??? Link to comment Share on other sites More sharing options...
Guest D's nuts Posted October 4, 2007 Share Posted October 4, 2007 idk Link to comment Share on other sites More sharing options...
rac74 Posted October 4, 2007 Share Posted October 4, 2007 Just curious...When using an oversized thottle, would there be a benefit to a restrictor plate? Link to comment Share on other sites More sharing options...
Terry Haines Posted October 4, 2007 Share Posted October 4, 2007 ...well the throttles on the A-M are after the restrictors and number 12 in total!!...I take your point that a form of restriction after the t/plate could increase velocity...but it all depends where your put it etc. Link to comment Share on other sites More sharing options...
BuckeyeSVT Posted October 4, 2007 Author Share Posted October 4, 2007 This whole "bigger ports" and more "port area" makes me wonder one thing. Plenum size. SVT intakes are a "compromise" design and have very little plenum area. Could the lack of plenum be the reason the ports are so huge? The newer 3L's have plenty of plenum (especially the newer dual plane ST220 style). The narrow ports would make sense due to the plenum size and amount of capacity of the intake itself. You don't need huge ports with a large plenum size. Correct? I'm thinking out loud here... anyone venture to input something "valuable"? -Dom Link to comment Share on other sites More sharing options...
rac74 Posted October 4, 2007 Share Posted October 4, 2007 I had wondered the same thing. The runners are acting like a plenum somehow. But then again, why didn't ford use an oval port with offset plenum like the 2.5L Jag? Link to comment Share on other sites More sharing options...
BuckeyeSVT Posted October 5, 2007 Author Share Posted October 5, 2007 Perhaps since the design came to them from Porsche in 1989 and they reworked it "compromised it" to fit I guess there was no real reason to change it. However, with any split port manifold - There is quite a bit of surface area they "fail" to see. Or perhaps that is the area they see and don't recognize how it hurts instead of helps. With dual runners it seems that certain CEG'ers think it's a superior design. Sure, look at the power on a heavily modified Hybrid with 11:1 compression. However ... as funny as this seems - They fail to realize how a split port design functions. Perhaps all this "port sizing" with the extremely gaping holes they can't understand why that is. It's for performance!!! Ermm.. well...not exactly. Split port design works in 2 ways. Essentially two manifolds in one. Short runners are for high rpm performance, long runners for low end torque. However with the SVT you essentially have no plenum - There's a very small area for plenum space (therefore the port sizes are huge). Think about this, long runners do nothing at high rpm. Too low velocity... Short runners kill performance at low RPM by low velocity (hence the secondaries to block them while inefficient under 3600RPM). Follow me so far? What makes me laugh my ass off at some people is that only the short runners are providing the real airflow for the top end and the long runners for the short. Pairing the two ports together actually hurts performance (two ports with differing velocities kills flow quality). Not to mention the surface area of both of the runners - hampers flow speed and overall velocity. It doesn't take a rocket scientist to see that both ports have a torque peak (long runners pops in around 2800RPM and short runners pops in at 5100RPM). No horsepower is gained on the bottom end because the short runner is shut off, however opening it earlier would still net even less because the manifold has to have enough RPM to flow efficiently. What does this mean? In a perfect world, the perfect "split port" upper intake would be the same - however the lower would have two sets of throttles - One for low end, one for top end. Think about it. Switch at the bottom for the short runners and pick up torque, open both in the midrange for maximum midrange and then shut the long runners at high RPM to keep the velocity difference and "bad quality air" from interfering with the high speed port. However there is a much simpler way of doing this without split port runners and the SVT manifold. That will be an experiment played out here in the future - Stay tuned for that. How other manufacturers deal with this is using a tuning valve in their upper intakes. A what? Ok, the LS and the Jag use what's called a Intake Tuning Valve (which in essence does exactly what I said above). It switches at mid rpm and changes runner length internally without having 2 different runner sizes... This would be the "better setup" instead of all that SVT crap. Throw that shiz away - Using it on 3L heads is stupid. I love it when people think "cut and paste" works for engines as well. This is my opinion... I don't do split port oval port engines. Anyhow, intakes aside I don't see issues with the intakes themselves. Perhaps a different camshaft and intake will breathe more life into the straight 3L. However, as this arguement started as a cheaper way for 3L's. Let's see where this all goes... -Dom Link to comment Share on other sites More sharing options...
Terry Haines Posted October 5, 2007 Share Posted October 5, 2007 ....but if a cam reprofile grinds metal OFF the base circle to give it more lift then the overall size of the cam lobe will be smaller...but have more lift??? ....but we are all told that the bigger dimension cams have more lift...and the reprofile makes it smaller...oh dear!!!!! Link to comment Share on other sites More sharing options...
Guest D's nuts Posted October 5, 2007 Share Posted October 5, 2007 ....but we are all told that the bigger dimension cams have more lift...and the reprofile makes it smaller...oh dear!!!!! Where the hell are you at? Ur like in left field somewhere lol cause I swear they're talking about intakes not cams....I could be wrong since Idont know anything though. Doesnt the upper intake go under the valve cover???? Link to comment Share on other sites More sharing options...
Terry Haines Posted October 5, 2007 Share Posted October 5, 2007 ....just a bad day I guess.Must be all these increased lift SVT cams flying around...sorry. Link to comment Share on other sites More sharing options...
Guest D's nuts Posted October 5, 2007 Share Posted October 5, 2007 Lol damn wheres the herbal meds at??? We need a smily face chiefing hehe Link to comment Share on other sites More sharing options...
Adam98SVT Posted October 5, 2007 Share Posted October 5, 2007 Lol damn wheres the herbal meds at??? We need a smily face chiefing hehe LOL that would be funny Link to comment Share on other sites More sharing options...
BuckeyeSVT Posted October 5, 2007 Author Share Posted October 5, 2007 ....but we are all told that the bigger dimension cams have more lift...and the reprofile makes it smaller...oh dear!!!!! Where the hell are you at? Ur like in left field somewhere lol cause I swear they're talking about intakes not cams....I could be wrong since Idont know anything though. Doesnt the upper intake go under the valve cover???? If the upper intake goes under the valve cover I think your engine is one of the most "unique" engines out there.... -Dom Link to comment Share on other sites More sharing options...
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