rick_tj

Hey guys.

I had some spare time tonight to think, and of course, I thought about the money pit. The thoughts went along these lines:

As some of the members know, I like to machine stuff by hand. I was thinking about making some intake manifold spacers. I'm not sure what I'd space out though. I was thinking about:

The throttle body to the dynamic chamber 1/4" spacer
the dynamic chamber to UIM 1/4" spacer
the UIM to LIM 1/2" spacer

So, all together, 1" of spacers. What do you guys think this would do for performance/gas mileage? These spacers will be gasket matched with the manifolds, which will be gasket match-ported. Also among the mods will be a full true dual exhaust. But, I'd like this thread to focus on the spacers only. Oh, I'll be adding in an SAFC eventually as well.

Thanks
-Rick

TurboIIGuy

I thought spacers only made a real difference on Carburated cars?!?!?!
Hmm.....
Seems pretty odd that spacers would be needed inthe airflow...
I understand the use of them on a carb since it changes the atomization from the disperasal point of the fuel to the ingestion of it into the motor.

Tech_Greek

Exactly, I wonder if injector spacers would do any good though? :o

Makenzie71

Spacers vary the intake length. If it was only for carbed cars then mazda must have been nuts investing all that time in the VDI system...ducati and MV Augusta are guilty too...

Even if spacers were just for fuel atomization, two of our injectors are built into the manifold and the fuel is subject to the speed and density of the air flow.

rick_tj

Well that's great, but what do you guys think of the setup I have up there? Any good?

Makenzie71

Look for posts by or pm rotarygod. He's a flow-guru.

Intake tuning doesn't really make more power if it's free-flowing. Spacers aren't going to change how restrictive it is. Basically your lengthening it, and by doing so you're moving your powerband down lower in the rpm range.

BlaCkPlaGUE

Would it increase low end torque having longer runners with the spacers? what if the spacers were larger? interesting idea tho..

Makenzie71

Spacer design will not increase power anywhere...just move it.

rick_tj

I just know that with Rotaries, low end power isn't exactly plentiful. I'd like to have more power down low. I figure with that, and a high flow exhaust system to help out the top end, that'd be a win win situation. Though, this is an interesting topic.

Makenzie71

actually, the exhaust and intake are both part of a breathing system. Alteration to one effects the other. Tuning one end for benefit at a lower range, and the other end for benefit at a higher range, you'll end up with a flatter powerband with no significant gains anywhere.

Turbo II-FB

someone needs to produce a adapter/spacer to put the FD UIM on s4-s5 LIM

Makenzie71

how much do you want to pay for it?

RETed

I'd doubt if you'd see any gains.
Please show proof of predicted gains with dyno sheets before going any further...


-Ted

Aaron Cake

iTrader: (1)

More power down low would require longer runners, which would shift the entire powerband down.

If you are going to make spacers, then you need to make a bunch of them in different widths and dyno each one several times.

The Mazda manifolds are quite well designed and already use a number of tricks (variable length runners, primary/secondary throttle plates, dynamic chamber, valved intake ports, etc.) to try and maximize their efficiency. The effect of changing this with a spacer must also be taken into account.

alwayssideways

there is a general number im not 100 percent sure but i think for evry 1/4 inch of length of a intake (includes spacer raises the powerband 500 rpms) someone please correct me if im wrong

Tech_Greek

Yeah If I go unplug the VDI it makes a BIG difference...

- Tech

Snrub

iTrader: (1)

Rick, you might be able to increase lower end but you'd sacrifice top end - assuming you had any positive benefit. If you want better low end start saving your pennies for a 13BT.

alwayssideways: Increasing the length would lower the power band, not push it higher up.

YearsOfDecay

The S5's are available...... FEED makes one from Japan, and I saw another comapny somewhere that offered one... they are relatively easy to make yourself as well.... the Bolt patter of the FD UIM is close enough to that of the S5 LIM that you can just install lengthened studs in the s5 UIM to pass through the adapter and then modify the bolt holes on the FD UIM...

The S4's however.... They CAN be done, but its a much harder process.... the bolt pattern is so different that you can't just modify the bolt holes on the FD UIM, you'd have to actually cut into the runners....... what you have to do is make the adapter, then install studs in the top and bottom of the adapter to match the bolt pattern of each LIM.. Upshot is that nothing needs to be done to the FD UIM.. Downshot is that you HAVE to drill out the holes on the s4 LIM so that the studs will pass through and then make sure that the bold have a flat seating surface on the underside of the LIM mating surface.... and that requires that the LIM be off the car.

in BOTH cases, the center bolt that goes down through the top just has to be lengthened.. as it is the focal point for the whole operation and remaines unaltered...

I've made a couple FD/s5 adapters for people......

BUT.... i really want to make an S4/FD adapter, but, because I need BOTH the FD and S4 manifolds in my possession to to it, nobody's taken me up on it yet... everybody wants a "drop in" unit... and thats just not possible with an S4.

as for flow... I have no clue on what its going to do to the power curve... People wanted the adapters, i made 'em....

And don't start PMing me with requests to make S5 adapters only.... I WILL NOT DO IT UNLESS YOU SEND ME BOTH MANIFOLDS so that they can be gasket matched and the FD UIM properly modded and the studs installed...... there is no senss of me making an adapter custom fit to a gaskett and then you chucking it on a LIM and UIM that are not gasket matched... creates turbulence where the ledges are and thats retarded.. If you don't like it.. pay 300+ bucks for the feed from japan and leave me alone... i do it as a hobby not to make money.

YearsOfDecay

And Here we have our problem.... while somebody MAY make the spacers.... I highly doubt ANYBODY on this forum is going to make different length spacers and then Dyno each setup... as that would be pretty pricey.....

Aaron is right... you are not going to get much out of the runners that Mazda already hasn't...

HOWEVER....... If you were to make the spacers out of a heat resistant material, such as a phoenelic (sp??) resin...... THEN.. you could stop heat transfer between the sections.... that THIS might actually have a noticeable effect!!!!

YearsOfDecay

If you want a quick study in what runner length does to the poweband, go talk to one of the N/A guys thats switched from the stock FC intake system to the holly style injector t-body system..... They've gone from almost four feet of intake runners after the t-body to less than a foot after the t-body.... Makes INSANE power at around 9K... but under 4k.... you better keep that clutch slippin!!!!!!

Dude runs a 13b in a an old toyota at my local track with a haltech, the RB holly carb adapter LIM and the Holley Quad injector T-Body.... MAN that things SCREAMS.... but.... if he dogs it off the line.. he just lost like 2 seconds at the end of the track...

PP systems are the same principal, but with like 3 inches of runner length after the t-body.. but... going to the PP does things that make it not much of a comparison to the standard intake system.....

Merovign

What he said.

Especially on an NA, where outside cool air is brought in, keeping the intake manifold several degrees cooler will impact power in a nice way. The rule of thumb is that a 10 degree drop in intake temperature equals a 1% increase in engine power, obviously within limits.

I'd have to measure manfold temperatures over time and intake temperatures over time on a Turbo to see if it mattered much. If the intake air was hotter than the manifolds, then at best the spacers would delay the equilibrium of manifold/intake temps for a few/several minutes, which could add a few HP during short runs (drag/autocross), esp. if the manifolds are cooled between runs (good old bag-o-ice). In this case the manifolds are acting like a second intercooler (a good reason to have a TII or improved hood scoop on a car with an FMIC, I just realized).

On the other hand, if a really good FMIC w/ nitrous/water/CO2 spray kept intake temps below stock manifold temps, then insulating spacers would add HP, especially if cooled between runs, and/or had cooling airflow past engine or simply wasn't run for long periods.

I think the cost/benefit ratio is better with temperature management than with changing tract length for most people - though obviously the "super-short-runner" thing works for high-end drag-racing power - as anyone who's looked at musclecar dragsters knows.

But the temperature management probably won't require you to have control over fuel curves and ignition and rev limiters the way a short-runner intake probably will, and there's that whole $40 vs. $400 thing going on (plus fuel control, ecu, etc).

I do go on and on, don't I?

PS It's Phenolic, if you were curious. Phenol is a crystalline solid with some nasty properties, but mixed with other stuff it can make temperature-resistant insulators.

jediknight7

id be carful about a spacer between the throttle body and dynamic chamber, since the black plastic peice thats there has vacum passages in it.

if you want to have a better idea of what the spacers will do, read this:

https://www.rx7club.com/general-rotary-tech-support-11/heres-how-figure-out-intake-runner-length-199788/

its a dry reading but will tell you what will happen and what to expect.