When does the UIM, LIM & TB become a restriction?
#1
Missin' my FD
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When does the UIM, LIM & TB become a restriction?
Just as the title says, at what point does the UIM, LIM, or TB become a restriction in making power? I have been reading the thread about the GroundZero LIM and was wondering about this.
Is it a matter of "port matching" or is it much more than that? My car will soon be running 20 psi occasionally, and I was curious if having something done to either the UIM, LIM, or TB would be beneficial at those boost levels.
Thanks.
Is it a matter of "port matching" or is it much more than that? My car will soon be running 20 psi occasionally, and I was curious if having something done to either the UIM, LIM, or TB would be beneficial at those boost levels.
Thanks.
#3
I dunno about the LIM, but I'm fairly certain that the UIM causes flow restriction at higher rpms, around 6250 - 6500 rpm. And since hp = torque * rpm / 5252, getting restriction at this higher rpm is not only gonna hurt your torque curve, it's gonna rob ya of max hp. Thus, the drop in our torque curves. Demetrious, on the other hand, uses a different UIM, which I believe plays an important part in his nice torque curve...
#4
2/4 wheel cornering fiend
Originally Posted by FDNewbie
I dunno about the LIM, but I'm fairly certain that the UIM causes flow restriction at higher rpms, around 6250 - 6500 rpm. And since hp = torque * rpm / 5252, getting restriction at this higher rpm is not only gonna hurt your torque curve, it's gonna rob ya of max hp. Thus, the drop in our torque curves. Demetrious, on the other hand, uses a different UIM, which I believe plays an important part in his nice torque curve...
#5
Originally Posted by Kento
Umm...how exactly are you "fairly certain that the UIM causes flow restriction at around 6250-6500 rpm"?
#6
Super Snuggles
Originally Posted by Kento
Umm...how exactly are you "fairly certain that the UIM causes flow restriction at around 6250-6500 rpm"?
#7
Will u do me a kindness?
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Originally Posted by jimlab
Because they're guessing and not one of them has the sense to take their intake manifold to a shop with a flow bench to find out what it'll actually flow.
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#8
Constant threat
Generally speaking - a forced induction rotary engine is not going to have to worry about 'flow' all that much. Sure, one could increase the sizes of all the aforementioned componenents but...what good does that do? It is not like the turbos can't ram enough air into the damned thing already.
Yes, I agree that theoretically there has to be some point where size would make a difference (keep your thoughts clean now...) but I don't even a widely modified rotary is going to start losing much performance....unless you were trying to get like 1000 hp out of one or something.
Yes, I agree that theoretically there has to be some point where size would make a difference (keep your thoughts clean now...) but I don't even a widely modified rotary is going to start losing much performance....unless you were trying to get like 1000 hp out of one or something.
#9
there is no dobut that a custom, goal specific manifold upper and lower would be better. how much? dont know. the stocker will have some compromises due to the fact it was for the street and had 255hp in mind.
#10
Originally Posted by the_glass_man
Seriously if you're that concerned with it, just take it some place with a flow bench, and have it tested. If you don't think it's flowing enough, port, polish, extrude hone it and your all set. You could get the new Ground Zero LIM, and a J-Tech UIM, or switch to an RE manifold if you feel like spending more money and want to get creative. Might as well upgrade the throttle body while you're at it.
#12
Rotary Enthusiast
I measured 30" h20 (1 psi drop) from the elbo before the TB, to the bottom of the uim where the pressure nipples are. This was at 7500 rpm and 9-10 psi boost, with the secondary valves in place.
#13
Super Snuggles
Interesting, however CFM through the intake runners is what would tell you whether there's a restriction or not at a given pressure level. Is the pressure drop still 1 psi at 15 psi? 20 psi? 25 psi? Measuring the volume of air getting through tells you when peak flow has been reached.
If you calculate the volume of air that the turbo(s) are capable of producing at a given boost level and compare it to the maximum flow of the intake after being tested on a flow bench, you'll find out whether or not the intake represents a restriction or not.
Note how flow pressure rises as the port becomes a restriction in the chart below. Also, note how flow (Corr CFM) tapers off as the port becomes a restriction. This is what we're looking for here.
If you calculate the volume of air that the turbo(s) are capable of producing at a given boost level and compare it to the maximum flow of the intake after being tested on a flow bench, you'll find out whether or not the intake represents a restriction or not.
Note how flow pressure rises as the port becomes a restriction in the chart below. Also, note how flow (Corr CFM) tapers off as the port becomes a restriction. This is what we're looking for here.
#14
Living life 9 seconds at a time
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It will benefit you when your making over 550rwhp with a large single turbo, but mainly for drag racing purposes. Your powerband will extend quite a bit. Demetrios carries his power through 9500rpms with just a street port.
I'll be dynoing my CYM in the next couple weeks. At first Demetrios and I will tune it for 15psi on pump. Gonna wait till spring for the race gas and 33psi. But in any case I'll post my results as I have the J-Tech upper and lower intake manifold and 80mm accufab throttle body.
I'll be dynoing my CYM in the next couple weeks. At first Demetrios and I will tune it for 15psi on pump. Gonna wait till spring for the race gas and 33psi. But in any case I'll post my results as I have the J-Tech upper and lower intake manifold and 80mm accufab throttle body.
#15
Rotary Motoring
iTrader: (9)
The Ground Zero LIM is probably designed to fix the flow imbalance between the front and rear 2ndary runners in the 3rd gen manifold.
I have been told it has been measured at up to 12% difference.
Does the front or the rear rotor usually let go on a 3rd gen that detonated...
I have been told it has been measured at up to 12% difference.
Does the front or the rear rotor usually let go on a 3rd gen that detonated...
#16
Rotary Enthusiast
Originally Posted by jimlab
Interesting, however CFM through the intake runners is what would tell you whether there's a restriction or not at a given pressure level. Is the pressure drop still 1 psi at 15 psi? 20 psi? 25 psi? Measuring the volume of air getting through tells you when peak flow has been reached.
If you calculate the volume of air that the turbo(s) are capable of producing at a given boost level and compare it to the maximum flow of the intake after being tested on a flow bench, you'll find out whether or not the intake represents a restriction or not.
Note how flow pressure rises as the port becomes a restriction in the chart below. Also, note how flow (Corr CFM) tapers off as the port becomes a restriction. This is what we're looking for here.
If you calculate the volume of air that the turbo(s) are capable of producing at a given boost level and compare it to the maximum flow of the intake after being tested on a flow bench, you'll find out whether or not the intake represents a restriction or not.
Note how flow pressure rises as the port becomes a restriction in the chart below. Also, note how flow (Corr CFM) tapers off as the port becomes a restriction. This is what we're looking for here.
For a simple orifice, 2x the flow means 4x the pressure drop.
Yes, it would be best to flow-bench test the manifolds and TB at true cfms. But with some correction for gross changes in flow area, installing nipples and measuring drops in the intake path on a mustang dyno would allow you to quickly find restrictions. 2 psi less drop in the intake system is 2 psi less at the turbo, and 3+ less at the exh manifold.
Your data shows flow at a constant 1 psi drop, as I understand it. I guess you know if it's port or valve diameter limited ... can't tell from just this data sheet. Either way, it doesn't really tell how much the ports will flow, since the max flow achieved will be proportional to the sq-rt of the pressure drop used in the test. It will clearly show how one head does compared to another tested at 28".
The "flow pressure" does not rise as the port becomes restrictive. As I see it, it is directly proportional to flow, and is likely a pitot type press meas't in the flow stream.
Last edited by KevinK2; 12-03-04 at 06:38 PM.
#17
Super Snuggles
Originally Posted by BLUE TII
The Ground Zero LIM is probably designed to fix the flow imbalance between the front and rear 2ndary runners in the 3rd gen manifold.
I've yet to see figures that back their claims.
#18
Rotary Motoring
iTrader: (9)
You know, it's funny that Mazda produced an intake manifold with a significant flow imbalance for nearly 10 years and the first I heard about it was when someone made a replacement...
#19
Originally Posted by jimlab
If you calculate the volume of air that the turbo(s) are capable of producing at a given boost level and compare it to the maximum flow of the intake after being tested on a flow bench, you'll find out whether or not the intake represents a restriction or not.
Originally Posted by jimlab
You know, it's funny that Mazda produced an intake manifold with a significant flow imbalance for nearly 10 years and the first I heard about it was when someone made a replacement...
I've yet to see figures that back their claims.
Last edited by FDNewbie; 12-03-04 at 07:16 PM.
#20
2/4 wheel cornering fiend
Originally Posted by FDNewbie
This goes along w/ what I wrote above. Not to say that the aftermarket scene hasn't made great products for the FD, but to me it seems that some crucial main steps were never taken in the past DECADE (which is a LONG time), and we're just now starting to address these issues (like the stock manifold, UIM & LIM restriction, etc)
#22
Super Snuggles
Originally Posted by SPOautos
Getting a max cfm rating doesnt tell you about pressure wave tuning and what rpm range the manifold is tuned for or most efficient at.
#23
Hey, where did my $$$ go?
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It is relevant, you just want to make light of it since you didnt think of it....pretty common with you.
Next you'll be telling us that manifolds arent pressure wave tuned and more efficient at certain rpms....and that it doesnt matter for turbo car...or something to that effect I'm sure
Next you'll be telling us that manifolds arent pressure wave tuned and more efficient at certain rpms....and that it doesnt matter for turbo car...or something to that effect I'm sure
Last edited by SPOautos; 12-03-04 at 08:11 PM.
#24
Super Snuggles
Originally Posted by SPOautos
It is relevant, you just want to make light of it since you didnt think of it....pretty common with you.
#25
Originally Posted by Kento
Maybe it's because the car hasn't really been sold in any real numbers for over a DECADE, so no aftermarket manufacturer would be willing to spend the money to develop a product that would have LITTLE RETURN on their investment relative to something for any number of other more popular cars...
If that's not what you're saying, and you're saying that it's just now starting to sell a lot, you think the FD aftermarket product market is at it's height right now? I find that interesting...I couldn't tell you myself, since I've only owned the car for 2 years.
If your point was neither of these, well, my bad lol. Explain