8 Throttle Body Intake

[Damien]

I don't think the numbers carbontech had looked too impressive but Tony Miller's site has some dyno sheets of their setup with cams that look great. I'll be doing some mild cams in a few months and want a better throttle response which is why I'm attempting this.

I had a 5 speed supra gearbox fitted almost 2 years ago and it's a fantastic car to drive so once I sort out the gremlins with the throttle bodies it should be a cracker.

 

[Damien]

Bit of an update. After doing more reasearch the lower apparent vacuum is inherent with all ITB setups because the intake stroke draws in air from the other cylinders through the vacuum hoses lowering the vacuum that the MAP sensors sees. From what I've read on a few Honda forums where ITB's are popular with Civics etc is that they use TPS or a combination of TPS and MAP with TPS as the input for low-mid throttle openings.

Turning out to be a big PITA as I can't tune using TPS and at idle it's only seeing 10-12inches of Hg instead of closer to 30 so I've lost over half the resolution. I might be able to get a custom firmware from the MAP-ECU guys though which would help.

Take home lesson is to ensure you can tune using TPS or preferably a combination of TPS & MAP.

 

[Peewee]

Are you sure you can't tune in TPS?

Most ecu's have this option. Even the Delco/Kalmaker has this option.

My Microtech flicks to a default IDLE fuel map when ever the TPS is <3% open.
Check to make sure the MAP-ECU doesn't do this.

 

[Damien]

I'm just emailing the MAP-ECU guys so I'll ask. I definitely haven't seen anything in the tuning software so far as it only seems to use TPS for enrichment on quick throttle openings.

 

[shadetree]

The easiest way to deal with the vacuum situation, and it's really not that hard, is to just tap a source off of each runner, to a separate container. Then you could even mount the MAP right off of that. Anything that needs vacuum gets hooked to the "vacuum canister" (that's what I decided to call it ).

I think thats a good name for it, but the store bought ones are called vacuum manifolds.
http://shopping.lightningmotorsports.com/catalog/Golden_Eagle_Vacuum_Manifold-p-138.html

Bit of an update. After doing more reasearch the lower apparent vacuum is inherent with all ITB setups because the intake stroke draws in air from the other cylinders through the vacuum hoses lowering the vacuum that the MAP sensors sees. From what I've read on a few Honda forums where ITB's are popular with Civics etc is that they use TPS or a combination of TPS and MAP with TPS as the input for low-mid throttle openings.

Have you considered putting check valves on each line before they join at the vacuum manifold? I would think that would work pretty well. Fish tank check valves work well, and are cheap.

http://www.petco.com/shop/product.aspx?sku=258113&cm_ven=lnk&cm_cat=82&cm_pla=258113&cm_ite=258113&SiteID=bvKXuUcaFDs-JgIaphqhmhupwD96IK6Bfw&CMReferringUrl=

 

[Damien]

Yes, I had thought of that but air needs to flow both ways so the MAP sensor can see the change in pressure. I'm getting about 12 inches of Hg at idle now and I have a custom firmware for the MAP-ECU which only goes to 15 inches so I have a lot more resolution. Idle is a bit rough as I'm yet to balance the throttlebodies before I start to tune it.

 

[shadetree]

You are right. The check valves are a bad idea. I did not think that thru.

I don't really see why the map sensor would be seeing so much lower vacuum with ITBs than with a standard intake manifold.

"lower apparent vacuum is inherent with all ITB setups because the intake stroke draws in air from the other cylinders through the vacuum hoses lowering the vacuum that the MAP sensors sees"
How is that any different than the condition in a intake manifold plenum? I would think you are not seeing as high vacuum because TBs do not have an air tight seal, having 4 or 8 of them creates alot more area that leaks.

Do you have the IACV hooked up to the vacuum manifold? That would probably help start up idle.

 

[Peewee]

You can't have an idle valve as well as ITB's.

 

[Damien]

I've tried it with and without the IACV and with it connected the vacuum is much worse when it opens. You are right that there are a lot more leaks but it's the apparent vacuum that the MAP sensor sees which is different - the vacuum under the butterfly is still pretty much the same. The problem is that the thin tubing can't pass the air through past enough for it to suck all the air out in each intake stroke.

Bigger tubing should help which is what I was going to do but I can't find the right pneumatic fittings in the size I want. When I was emailing the guys at MAP-ECU about it they'd previously done an ITB setup on a BMW and used a balance tube of 19mm ID welded to 10mm holes on the intake and said that worked very well. Compare that with the 4mm tubing I'm using and it starts to make sense. I've got a good compromise now with short lengths of 4mm ID tubing connecting to a central tube of 8mm ID aluminium. Once I've worked out the best method I'll post some pics.

 

[shadetree]

You can't have an idle valve as well as ITB's.

Yes, you can. You just have to make an adaptor plate for it. One port is attached to vacuum manifold, the other is vented.

http://www.honda-tech.com/zerothread?id=1335398

http://www.honda-tech.com/zerothread?id=947796

 

[Peewee]

So basically you use the MAP line as an ISCV line?

I would have thought that the MAP line would have been too small to flow enough air for idle, and if you made it bigger to flow enough air, the MAP signal would have been compromised?

 

[Damien]

That's what I've found - it compromises the MAP signal. You could run a dedicated set of idle air lines into the throttlebodies though.

 

[shadetree]

Run a line from each intake runner to a vacuum manifold.

Run lines to all systems that need a vacuum source from that manifold...brake booster, IACV, MAP, FPR.

 

[Damien]

I started down that route but I'd need much bigger tubing than the 4mm ID to get enough vacuum in the vac manifold. Also, as soon as the IACV opens the vac pretty much disappears. You also need a big tank to stabilise the vac with all those things connected and some guys I've spoken to needed a 5L vac manifold when they fitted ITB's to a GM V8.

I've ordered an electric vacuum pump designed to use on eletric cars for providing vac to the brake booster. I'll connect the brake booster, PCV, VSV and charcoal canister to the pump and the MAP sensor and FPR to the vacuum manifold. Starting to see light at the end of the tunnel

 

[Peewee]

Thats the identical setup I plan to do when I justify the funds.

 

[nzsimon]

mine

heres how I did mine maniflod bolts to the two holes in the rear water runner

 

[Damien]

Very neat work - looking great!

 

[Peewee]

You finally got the Carbontech setup working?

 

[Damien]

Nearly there actually. Got it idling smoothly and the MAP pressure is stable so I can start sorting out the fuel next weekend... been struggling to find time lately.

Here's how it's looking so far. There's a plate that bolts on top which will form the base of the plenum and I have short trumpets which bolt to the plate. It'll all fit under the bonnet.

 

[nzsimon]

filter

What air filter are you using a common one ?

I have thought about making a plate that bolts under the trumpets