Stock Throttle Body adapter Plates 60 & 64mm to 70mm IM

[Keoman]

Well, first I will say this is just an idea I had that I would like to share and get feedback. Reading about (and experiencing!) the problems it seems to cause, mating a stock 60mm TB to a larger bore (68mm, 70mm+) intake manifold, leaving voids where air passages should be sealed. Symptoms seem to be idle problems (vacuum leaks). Ask me how I know...
Has this already been done? Is there an easier way! (besides spending $100+ on a new TB!)

I made printouts of both 60 and 64mm TB, however I'm not sure the ITR TB's experience the same mating problems.

Material is 1/4" thick aluminum. I plan to replace all hardware with longer bolts. IACV feed hole will be drilled when fitted to IM.

 

[Taco]

Are you an engineer or a machinist?

Either way are you planning on mass producing this, or just making it for yourself?

 

[Keoman]

First, I'd like to make one and make sure it solves my problem. I could have them produced if there is a demand.

 

[NemesisCBR]

I have yet to come across reading about this issue but im not saying its non existant. Heres my question though. If you have a intake manifold thats got a bore that large its probably for high breathing applications. If thats the case why would you be running a 60-64mm tb? I would assume youd run a larger tb and then you wouldnt have this issue at all.

I dont see why an adapter plate wouldnt be a solution. Maybe a hondata tb gasket even? Or seal up the passages on the tb if they arent in use.

 

[XjoEnX]

The best way to avoid it would just be to invest in a matching diameter TB. An adapter plate could work for what you're doing though but you'd still have the worry of designing or having a gasket made for it to aid in sealing the leaks. It may be more trouble than its worth.

 

[Keoman]

Thank you for the feedback.
I am looking for the most cost effective way to approach this problem.
To answer your questions, No matter the gasket, it is not going to seal against air. Cutting out a custom gasket takes 2 minutes. Purchasing a 70mm TB is always an option, but remember, looking for cost effective. Have read quite a bit about the lack of idle adjustment in aftermarket TB's. Also, there is absolutely no need for a larger TB, the car is skiddishly fast and that's plenty for my DD.
I would have purchased a matching 60mm intake however I could not find a 60mm ebay cheapie at the time.

The intake bore does not need to be 70mm by any means. Engine is practically bone stock. I had to purchase an aftermarket intake so I could cut it in half so It would fit in my engine bay.
Pic

 

[NemesisCBR]

But the manifold bore should not be 70mm to begin with unless it was bored out by the previous owner. None of the itr clone manifolds for the b series are that large out of the factory that im aware of. Back to mention of gaskets, i cant find hondata's through a quick search and outlaw engineering sells them in a package with the im gasket it seems but i did find skunk2 thermal gaskets. From the image though it doesnt look like your manifold has been modified and any oem/aftermarket gasket should work with that and line up with the oem tb. To quote skunk2 which uses matching ports to the oem tb's, you can bore the tb opening to 70mm but they arent that big to start with.

http://www.jhpusa.com/store/pc/viewPrd.asp?idproduct=11395&idcategory=617


Perhaps im not understanding your problem. Theres only 1 port on the manifold, the rest are bolt locations. If for some reason you arent using that port the way the motor is normally hooked up then i could see a vacuum issue coming up. You may need to provide more detail on your idle problem or whatever it is cus im more inclined to believe those that have had issues did something wrong or werent looking at the correct problem, ie iacv, tps etc.

 

[XjoEnX]

I had completely forgot about your build. In any case, it's worth a shot. You already went to the extreme to make the IM fit in there and it's a clean cut.

If its a piece you're making on your own then best of luck and I hope the outcome is perfect for what you need. It looks like all you need to do is make sure the surface areas between each connecting pieces are completely flat to match up. :thumbs up

 

[Keoman]

This is a quote off of skunk2's website for a B-Series GS-R Pro Series Intake manifold:

Note:
Ideal for turbocharged and naturally aspirated applications.
Eliminated secondary butterflies for improved airflow and horsepower.
70mm throttle body opening can be port-matched up to 74mm.
http://store.skunk2.com/pro-series-intake-manifold.html

The information you quoted is no longer accurate. I read in another thread that they changed because of enormous customer request for 70mm bore IM's.

THe IACV feed port is being used as normal. If you look at the face of the 60mm TB, you will see air passages around the bore of the TB. These passages are not sealing because of the 70mm mating surface on the IM. By creating an adapter plate, the TB will mate with a 60mm hole like honda intended, thus eliminating the leaks.

Got the material for the plate from a buddy of mine today, going to go up to the university tomorrow and knock this out on the mill.

This is a very infomative quote from m4xwellmurd3r from honda-tech:

I don't think a bigger throttle body is needed on our cars. 60mm is plenty big.

When you get a bigger throttle body, what is generally percieved as an increase in throttle response, is actually a decrease in throttle control. By adding a bigger throttle body, you are lowering the point at which the engine is breathing at 100%. So instead of 100% throttle opening being WOT, 60% is now WOT. the last 40% do nothing.

There's a post on HybridZ about a member that switched from a stock 50mm TB to a 60mm TB, and megasquirt was showing that at 60% throttle, it has atmospheric pressure (WOT condition) (btw that's on a 2.8L inline 6 engine. They make PLENTY of power using a stock TB)

I would upgrade the throttle body last. I like the idea of an adaptor for the stock TB to a bigger intake manifold to get a better seal, but I think what would be best is also find a way to smooth the transition between the two, for airflow sake.

one other thing I should point out with the whole TB debate. I have a B18 with a ported LS head, and jge 303 cams (.417 lift 274 duration) And i get full throttle BEFORE my foot is to the floor. I noticed this just from driving a lot, that the last little bit of my throttle actually doesn't do anything. I wish I had s300 on my car to really see it in numbers, but I think even the stock 60mm unit is plenty big.

Last upgrade in a build should be the throttle body. It makes no sense to throw some monster on the car, and sacrifice the fine throttle control.

 

[Keoman]

Well, it didn't work.
The design was perfect. Gave the TB a nice concentric surface to mount to however the problem persists.

 

[NemesisCBR]

So the problem exists elsewhere?

I wasnt aware that the current pro series manifolds were 70mm. I should say paraphrase rather than quote cus i was indicating the 70mm range was still used and to mention 74mm wouldnt have been relevant. If you have a 70mm version then i can see how that could be a problem on a stock tb. Mine is a earlier pro series and was smaller than 70mm.

 

[Keoman]

Yeah Nemesis, I honestly had no idea when I ordered the IM that it was a 70 and the problem it was going to cause. Anyways, that's fixed now.

Ordered a new O2 sensor. Sprayed the IM down with break cleaner again yesterday while it was started up hoping that I would find somewhere I had missed, finding the vacuum leak. Nothing.
If the IACV is unhooked while the car is running, the idle calms down a little HOWEVER, giving it up to 1/4 throttle causes the engine to rev and choke out, rev and choke out. I'll post a video a little later.
Also need to pull the plugs after its been ran.

 

[Keoman]

Video:

http://www.youtube.com/watch?v=KcstFtoFKKQ