Improving Head Flow-Cams,Valves,P&P,Manifolds,Etc - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-28-2011, 01:57 AM   #1
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Default Improving Head Flow-Cams,Valves,P&P,Manifolds,Etc

I wanted to to pull together a thread for trying to find out what would make the most improvement in air flow to the head on our Miata Engines using turbos.
Choices include Throttle body, Intake Manifold, P&P, Larger Valves, Camshafts, Exhaust Manifold, Etc.
For discussion purposes, lets not worry about which turbo, but the fact that there is air being forced into the engine. I believe the above components will have different value of importance in a turbo motor than a NA motor.


It seem to me that there would be a larger increase in airflow with an improvement in cams versus larger valves. Because the lift and duration would make a bigger difference than 1mm larger valves. Does anyone any data to back this up?
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Old 09-30-2011, 01:59 AM   #2
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Best to worst: intake mani, exhaust manifold, cams, ports, throttle body.

camshaft specifications is almost entirely derived from port flow.
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Old 09-30-2011, 02:36 AM   #3
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Isn't the stock intake manifold good enough for about 250 whp? From all the threads I've read after 250 it becomes a bottle neck however until that it's great.
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Old 09-30-2011, 09:05 AM   #4
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For those on a budget, there is enough room in the cylinder head that reasonable camshaft selection will net power. Not everyone will go through the trouble of cylinder head work.

Most people forget that bigger camshaft changes and gear selection go hand in hand.
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Old 09-30-2011, 11:02 AM   #5
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You made no mention of what this engine is going to be used for, everything you listed above is so general, and everything with engines is so complicated. I agree for the most part with Sav, except if you are optimizing a setup for a turbo and that requires using a larger plenum then you should also increase throttle body size so you dont loose engine response. And if you are looking to run high rpm's cams are very helpful.
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Old 09-30-2011, 11:03 AM   #6
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I've been curious about several different options for improving flow but it doesn't seem like there is much information out there showing what kind of gains to expect.

A conservative cam swap, something like the Mazdaspeed intake cam seems like it should net some decent power (http://949racing.com/mazdaspeed-miata-intake-cam.aspx), but as far as I know most of the quick cars around here are still running the stock cams?

I've also read a few posts about porting the stock intake manifold. It just seems like there is almost no hard data showing a performance gain. I know FaeFlora said his car was running lean after the intake mani port but that seems like the only information I've seen to indicate that it made any power.

I'd love to see some information from some of the quicker cars and what they are running. If only I had the disposable income to swap parts and make dyno pulls to compare.
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Old 09-30-2011, 11:21 AM   #7
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/\ The Mazdaspeed cam is a baby cam. It will work with stock ecus. If you are going with an aftermarket ecu, I do not understand why you would not go with a hotter cam than that.

I had a Web cam with a ported 95 head and stock valves and springs, and was able to get my car to break into the 13's on my N/A set up. It is a very mild, very streetable cam with only 214* duration at .050" lift. Lift is .370". Car still had great low end acceleration and pulled hard to 8000 rpm. I saw a big improvement when I switched to the 99 head and 1 mm over valves.

This cam would not work with a stock ecu, but almost everyone runs MS. Running a stock cam regardless of the options in my opinion is leaving way too much on the table.

I never could understand why more people on this site does not do more cylinder head and camshaft development. BPs wake the **** up with work in those areas.
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Old 09-30-2011, 12:34 PM   #8
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Thanks Sav,
I wouldn't have thought it would be in that order for a turbo'd 1.8. I would have thought it would be head porting or cams. Opinions on larger valves on the list? Not so much concerned about hp numbers for this discussion, just cost related to flow improvements. Lets say the bottom end has the usual stuff, pistons, rods, bearings, oil pump gears. Lets say we had a way to put 25psi through it.
If the intake manifold represents a chamber that is filled with pressurized air, wouldn't the restriction be greater in the port/valve area and higher priority should be in this area? It would seem that even small changes in flow in this area would yield greater flow changes than other areas.
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Old 09-30-2011, 02:11 PM   #9
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You need to go read up on intake manifolds, do a search there is so much more to it than what you are thinking.

Also for intake manifold gains, there are dynos out there, I have one on my wed site under intake manifolds, check it out.
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Old 09-30-2011, 02:58 PM   #10
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Quote:
Originally Posted by miata2fast View Post
/\ The Mazdaspeed cam is a baby cam. It will work with stock ecus. If you are going with an aftermarket ecu, I do not understand why you would not go with a hotter cam than that.

I had a Web cam with a ported 95 head and stock valves and springs, and was able to get my car to break into the 13's on my N/A set up. It is a very mild, very streetable cam with only 214* duration at .050" lift. Lift is .370". Car still had great low end acceleration and pulled hard to 8000 rpm. I saw a big improvement when I switched to the 99 head and 1 mm over valves.

This cam would not work with a stock ecu, but almost everyone runs MS. Running a stock cam regardless of the options in my opinion is leaving way too much on the table.

I never could understand why more people on this site does not do more cylinder head and camshaft development. BPs wake the **** up with work in those areas.
That's sort of what I was expecting. You see so many other cars that see great gains from cam swaps and the BP certainly isn't engineered to be a marvel of efficiency. It would be nice if some of you ballers could go out and experiment with what works best.
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Old 09-30-2011, 04:18 PM   #11
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Very nice design Ryan. Did you have to use 3d modeling software of some kind to get what you wanted? Yes, there is a lot to know about intake manifold design. Part science, part black arts, shovel load of experience. Would you agree with Sav"s order of appearance on improvments?
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Old 09-30-2011, 07:09 PM   #12
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Quote:
Originally Posted by triple88a View Post
Isn't the stock intake manifold good enough for about 250 whp? From all the threads I've read after 250 it becomes a bottle neck however until that it's great.
IM's are not really hp limited. They just give you a particular torque curve shape when in full boost.

IM's operate in boost so the volumetric flow rate is the same, regardless of boost. The *mass* flow rate is what increases with boost. Resonances occur the same way whether NA or boosted. Look at VICS - ideal switchover point is 5600 RPM whether both NA and turboed.

However some manifolds hold the flat part of the torque curve longer - i.e. are more biased to provide high RPM power. For example, hold flat torque to 6000 RPM instead of to 5500 RPM, and provide more torque at 7000. The EUDM 01 manifold is rumored to be like this.
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