smaller runner VS large runner on FI
smaller runner VS large runner on FI i dont really see anyone using a head larger than 225cc for a blower or turbo... i was just curious too know what a smaller runner would do for performance, psi, power curve VS a large runner like a ET 240 or ET 255...
in my eyes i cant see a huge 255cc head hurting a forced induction setup at all.... it will lower the boost which will inturn not make as much heat....
what really happens in this situation?
Thanks,
Tyler
in my eyes i cant see a huge 255cc head hurting a forced induction setup at all.... it will lower the boost which will inturn not make as much heat....
what really happens in this situation?
Thanks,
Tyler
Originally Posted by SuperZ
I think on a N/A car you want the smaller port for Velocity but From what i hear you want a large runner for F/I because velocity isnt a problem.Anyone?
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From: Norn Iron
I thought there were a lot of guys runnong 240 heads, like Allpro or ETP ??
225 is more common, as AFR etc make them off the shelf, so are easier to actually get your hands on a set.
I opted for a smallish cam, and the CNC'd 215cc Edelbrocks, for the smallish runners, to keep good port velocities. It is always in the back of my mind though...would a set of bigger heads work better ?? ( stock bore size though )
Trickflow's numbers look good....if they are comparable to how other heads are flowed.
Either way, mine seems to be working well.
225 is more common, as AFR etc make them off the shelf, so are easier to actually get your hands on a set.
I opted for a smallish cam, and the CNC'd 215cc Edelbrocks, for the smallish runners, to keep good port velocities. It is always in the back of my mind though...would a set of bigger heads work better ?? ( stock bore size though )
Trickflow's numbers look good....if they are comparable to how other heads are flowed.
Either way, mine seems to be working well.
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Verdad Gallardo Im sure any after market 215 or 225 runner works very well Im just not sure if 240+ is to much.Guess just depends on the cubic inch and amount of boost.I see alot of afr225s but I also see 6.0 heads go big number as well.
Originally Posted by SuperZ
Im sure any after market 215 or 225 runner works very well Im just not sure if 240+ is to much.Guess just depends on the cubic inch and amount of boost.I see alot of afr225s but I also see 6.0 heads go big number as well.
i know that having a good exhaust flow on a blower car is very important...
i just wish a "expert" would chime in...
Last edited by ty_ty13; Nov 8, 2006 at 09:06 AM.
My engine builder told me that there really isnt such a thing as too big of heads for a FI engine. The blower/turbo will fill the ports and cylinder heads. A smaller port would pose more of a restricition, therefore less filling.
As long as you match the cam correctly, I dont think going BIG would be bad at all. More air = more power. The easier it is for the blower to fill the motor, the more power will be made. I think he put it this way. "With smaller heads you can make big power on big boost, with big heads you can make the same or more power on less boost." Less boost means your getting better efficiency out of the blower as well.
The only issue I could imagine would be with small c.i. not being able to use the BIG heads at lower rpm's(low to no boost), therefore making the motor less streetable.
As long as you match the cam correctly, I dont think going BIG would be bad at all. More air = more power. The easier it is for the blower to fill the motor, the more power will be made. I think he put it this way. "With smaller heads you can make big power on big boost, with big heads you can make the same or more power on less boost." Less boost means your getting better efficiency out of the blower as well.
The only issue I could imagine would be with small c.i. not being able to use the BIG heads at lower rpm's(low to no boost), therefore making the motor less streetable.
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The worst effect might be a miniscule more time to fully spool (turbo), but that can be addressed in a good combo. FI doesn't seem to be affected by overly large induction like N/A. I'm using relatively small ports and restrictive (LS6) intake, so maybe I run a bit more boost, but the car still runs.
That's my take.
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That's my take.
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I am definitely no expert but I agree with FIRE67 here's why, I am a long-time mopar guy so bear with me on the example. There is an old expression "Hemi's love blowers" reason being is the the hemi heads have massive ports and huge combustion chambers think like 180cc's. the heads are waaayyy overkill for the engine even at 426 ci. the blower (at least a roots or twin screw) will pick up the velocity on the lower end and push with little restriction on the top end, best of both worlds. DISCLAIMER: this is not the only reason Hemi's show amazing results with blowers but it is one of the bigger one's.
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From: Norn Iron
Originally Posted by SS00Blue
I'm using relatively small ports and restrictive (LS6) intake, so maybe I run a bit more boost, but the car still runs.
That's my take.
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That's my take.
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Just to note- when you plug in the #'s to the boost equations (on turbobygarrett.com) - upping the engine VE a few percent (via bigger ports)- doesn't have that big of an impact on req'd boost for a particular horsepower level. I don't think you are really going to get into a much different efficiency island w/a higher VE head. Maybe if you combine that with a better flowing cam--- but even a 5% gain in VE - you are maybe looking at a couple psi drop with the increased VE.
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Originally Posted by stevieturbo
Not really sure you can say the LS6 intake is restrictive..when there are people making 1000+ with it.
That's my point.
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From: Norn Iron
Originally Posted by SS00Blue
Compared to a GMPP carb intake with a SM elbow the LS6 intake is wildly more restrictive. 1000+ hp is great (that's about where I am) but it requires more boost to get there.
That's my point.
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That's my point.
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I know I am using a custom elbow and the Edelbrock Victor Jnr.
Im still not convinced it has any huge benefits over the LS6/stock TB I was using.
I dont have access to a dyno...but feulling requirements between the 2 setups, changed very little. Biggest changes were in the mid-range, top end was very little different at all.
Perhaps cam plays a big part there too ???? Mine would be relatively mild.
I think alot of the people that use the carb style intake mannies use them to get nearly perfectly divided airflow between the 8 cylinders. With the LS1 style intake the back 2 get alot more air as EVERYONE knows. It also will give u some more power but i think alot of that has to do with the air not having to make alot os 90*turns like it does with a LS1 style intake.
As far as teh heads. Im sure like everything else too big is too big. Having larger runners im sure helps when u go from stock heads to AFR's or the like but it aint like u should jsut get the biggest CC runner u can and ull make the most power. Most of the people in FI on LSX engines use 225's. I wish some of the big names would drop in and say when is too much. GL
John
As far as teh heads. Im sure like everything else too big is too big. Having larger runners im sure helps when u go from stock heads to AFR's or the like but it aint like u should jsut get the biggest CC runner u can and ull make the most power. Most of the people in FI on LSX engines use 225's. I wish some of the big names would drop in and say when is too much. GL
John
I chose PRC stg 2.5 LS6 CNC'd heads with 2.04/1.57 valves 235CC runners. Not really worried about port velocities. My blower is always pushing air at any rpm... 
I will have results soon..
I will have results soon..