Double Throttle Bodies

[ToranaJudd]

Came accross this Pic, How is this done and it it practicle for Twin Turbo?

http://img346.imageshack.us/img346/8743/baydone025kw.jpg

Cheers Judd

 

[ed_ma61]

pm Peewee...

 

[Peewee]

Yes, thats mine

A better/closer pic for you

Basically I bought a second manifold, and had my machinist make what you see.

The thing is that the 2nd TB is actually upsidedown, in order to put the linkage on the same side, and simplify the setup.
The 'snout' was welded up upright, but the flange was cut off, and welded on upsidedown, in order to do what I asked.

As for FI, I don't know, as I didn't have it made for FI.
But I've been told that for FI you should put some sort of barrier down the middle.

 

[Cobra]

This is a twin Turbo/Twin t/b setup in a Cobra

 

[Zuffen]

Edz has a similar plenum for his EH Holden build up.

 

[WDoherty]

if you are going n/a i can't imagine why you would need another throttle body. Ours is pretty large i think 70mm and ls1's make over 400rwhp on an original throttle body (which can't be that much bigger b/c i know it was a big deal that the ls2 went to a hugh 90mm) so for the n/a flow capacity of this engine, i can't see any benefit.

 

[Peewee]

Go drive a car with twin TB's and you quickly realise why people want them.
Sure, on stock cams they won't produce any more power, but the midrange response compared to stock is awesome.

 

[Lextreme II]

Peewee,

I was thinking of make three cuts on each intake and the front and rear portion stay. The middle section will be half again and use the TB size and flip it over. Then you will have two isomeres TB. What do u think?

 

[Peewee]

It would work, but its a LOT more welding

 

[WDoherty]

what car do you have that in, does the engine have other mods, do you feel it helps out much? It just surprises me b/c i see engines that are much larger and more powerful using a similiar diameter single throttle body.

 

[Peewee]

Car is a 1984 Soarer. Motor is internally stock, with that manifold, custom extractors, manual trans, and aftermarket ecu.

As I said before, it will do nothing for peak power on stock cams, but the throttle response in the midrange is much better.

Its like going ITB's (to an extent), they probably won't help get you any more power on paper, but the drivability is much better.

 

[Lambo]

Dual throttle bodies

The locals here cut two manifolds down the middle front to rear and welded them back together for their twin turbo 1uz f40 tried to find a pic but only came up with their latest version still nice to look at, also snapped this on the weekend a 1uz in a local Countach replica.

Regards
Lambo

 

[Glen75]

Go drive a car with twin TB's and you quickly realise why people want them.
Sure, on stock cams they won't produce any more power, but the midrange response compared to stock is awesome.

Do you think that is due to gain volumetic effiecency or just due to have more cross section of butterfly open at half throttle? If the latter, couldn;t the same be acheived by having a diffent shaped "cam" of the throttle cable linkage?:shrug:

 

[rivmasta]

Do you think that is due to gain volumetic effiecency or just due to have more cross section of butterfly open at half throttle? If the latter, couldn;t the same be acheived by having a diffent shaped "cam" of the throttle cable linkage?:shrug:

I ran the numbers through EAP on a stock engine

with 1 TB @ 88mm Vol Eff maxed at 80.6% @ 4500 rpm
with 1 TB @ 100mm Vol Eff maxed at 81.0% @ 4500 rpm
with 2 TB @ 88mm Vol Eff maxed at 81.8 @ 4500 rpm

With cfm's of 969, 1247 and 1939cfm respectively I would have expected a larger pickup than this... stock cams though... yawn...

however ran it on a modified engine (rally hi torque) and the vol eff changes from 96.7% at 6000 to 98.9%. It also picked up 4pd torque at 4500rpm and 12hp at 7000. this was a single 100mm compared to twin 88mm. This high in the scale a change of 2.2% in vol eff must be a fair bit more mixture in the chamber!

At the end of the day though, this is a simiulation only - what it doesnt take into account is airflow disturbance inside the plenum from 2 opposing columns of air coming in increasing or decreasing intake runner velocity. You'd have to flow bench for accurate numbers, but it seems very plausible to me that vol eff would pick up by a substantial amount in line with a substantial more amount of cfm.

 

[Lambo]

Dual throttle bodies

Hi Guys, Maybe you can answer this one for me, i am toying with doing the twin throttles bodies for twin turbos, i was hoping to use the stock computer with an injector upgrade with maybe a piggyback of some kind, i only want to run 7-8lb boost ,but i figure the flow from 2 turbos would overload the original AFM, i assume the above 2 intakes can't be done with a stock computer because only one side will have an afm, so how does the computer know about the extra air from the otherside, or do i have to do away with the afm altogether and run aftermarket, maybe there is a clever way of running 2 afms , divide the intake pelum and then each afm only sees 1/2 the air flow,and run 2 stock computers, each one running a bank of 4 cylinders, provided the crank trigger and camshaft triggers could go to both computers, i believe thats what BMW did for the early v12 it had 2 separate computers one for each bank. Another idea would be to have a circuit that takes the voltage and frequency from the AFM and effectivly 1/2 s it, or somehow combines the 2 outputs that are feed to the ECU so you could then run 2 afm,s Any thoughts.

Regards
Lambo

 

[GSMnow]

The toughest part about using two intake tracts is that they probably won't balance perfectly. As long as it is a single plenum, then a MAP sensor based ECU will work fine, but AFM systems will be a problem. If you used 2 MAF sensors (The early Lexus sensors are Karmen Votex air velocity meters, but that is not critical here) and add the outputs together, (this takes a micro controller as the signals are pulses at a frequency proportional to air flow rate) it would give the frequency for all the air that entered. This would probably need some type of look up table to correct the mixture across the flow range as the air flow rate to frequency is not perfectly linear, and the AFM also measures the air temp to correct for air density. Most twin turbo cars that I have seen that use AFM sensors draw all their intake air through one sensor just for this reason. The HKS VPC (and others) use a MAP sensor and rpm based lookup tables to generate a new AFM signalfor the ECU and elimintae the AFM completely. This would be a good setup for a turbo conversion as it eliminates the flow limitation of a stock AFM.

Gary M.

 

[Lambo]

Thanks Gary, that helps alot, the biggest problem as i see it is the extra flow of twin turbos through the single AFM i'll have to investigate away around that, but it's starting to look like MAp and aftermarket is the way i may have to go.

Regards
Lambo

 

[GSMnow]

Any time you add boost of more than about 6 psi on any non turbo motor, I have to recomend a new ECU. Either a factory ECU that knows boost, or a programmable system. Piggy back controllers and rising rate regulators can work up to about 6 or 8 psi, but beyond that,m you need a boost ECU. I built turbo systems for 3 cars from scratch. All of those were just 4 bangers, but the same issues always come up. My Celica 22RE and one of the Civics (a 1.5L cingle cam) had Electromotive TEC ECU's already and it was a simple matter of changing the MAP sensor to 2 Bar, installing bigger injectors, and then dialing in the fuel and timing maps with the new found boost. The other car owner was certain his fuel system was up to the task for boost. Is was a chipped stock Honda ECU on a ZC motor. He was still using a stock MAP sensor. The Honda MAP sensor does give a climbing voltage out to around 9 psi of boost, but as soon as it hit 2 psi or so, the injectors cut out and the Check Engine light came on with a MAP sensor error code. He tried all of the tricks to keep the MAP sensor from seeing boost and of course it just went lean. I finally talked him into a rising rate fuel pressure regulator and I got it dialed in. It went a bit too rich around 6 psi and leaned out again as he topped 10 psi. The car ran strong, but he was not happy as the other Civic ran away from him. He then tried to tune it himself. He cranked the boost to 13 psi like the other Civic, removed the rising rate regulator because his fule pressure was going to 75 psi and the pump blew fuses. He put in bigger injectors and it would not idle because it was so rich at light load. But when he went into boost, he proceded to blow the head gasket and crack all four pistons. because it went dead lean by 4 psi of boost. Doh!

Fuel control is very important under boost.

Gary M.