First off, I want to apologize for the spam. Three of the topics on the first page are mine now, lol
And as some of you know, Ive was working on mating an Eaton M90 from a 3800sc to my 2.8. I started making the manifold, then my one of the rods in my 4.0 Explorer decided it wanted to see the world outside the engine block. So it liberated itself, and the fiero became my daily Now I probably shouldnt be ghettocharging my daily. But Im still itching for a performance boost of some sort. So I thought, why not take the manifold I started making, and convert it to twin throttle bodies, sort of like a lambo?
You can see the tubes I bolted to it. Ill just cap one end of each, and put a throttle body on the other. When I get a new daily and resume the blower project, Ill just make new ones.
I did some math, and the area of the opening on the stock 52mm tb is equal to that of two 36mm throttle bodies. Id probably have to get these from a motorcycle or something, since I cant find any cars with that small of one. but then how would I make the tps work? Anywhere from 36-40mm would be a good size probably, so if any of you know where I could get them used/for cheap Id appreciate the tip!
------------------ I have no idea what Im doing, but Im doing it.
The 2.8L dual throttle body has been done before and was sold on this forum for a while. It most likely makes the engine breathe better but installing one will upset the TPS readings. The ECM is programmed for TPS readings of between .5 to 5 Volts. Each TPS % opening position for engine conditions corresponds to a given point that the ECM is expecting to see. Dual throttle bodies will give twice the amount of flow at a TPS voltage reading intended for half the flow. This will cause your engine to run lean and that's not good. You can use such, but an ECM reprogramming (New chip program) should be necessary.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The 2.8L dual throttle body has been done before and was sold on this forum for a while. It most likely makes the engine breathe better but installing one will upset the TPS readings. The ECM is programmed for TPS readings of between .5 to 5 Volts. Each TPS % opening position for engine conditions corresponds to a given point that the ECM is expecting to see. Dual throttle bodies will give twice the amount of flow at a TPS voltage reading intended for half the flow. This will cause your engine to run lean and that's not good. You can use such, but an ECM reprogramming (New chip program) should be necessary.
My thought was that if I have two smaller throttle bodies that flow the equivalent of the stock one on its own, I wont need to adjust anything. Although Im gonna have to buy a chip burner for the supercharger build, so I may as well just get it sooner
The ECM uses the TPS to know if the throttle is closed or if it moves open quickly and an "accelerator pump shot" of additional fuel is needed. The ECM doesn't use the TPS to determine how much air is flowing. It mainly uses the MAP sensor to determine how much fuel to inject.
Several years ago, I canvassed the local salvage yards looking for throttle bodies smaller than 52mm. I couldn't find any (the one exception being the 3-banger in the Geo Metro, which is TBI so it doesn't really count).
Also keep in mind that the engine only has one cylinder sucking in air at a time. So if you have a common plenum (like the stock V6 intake), that means each cylinder is being fed by a 52mm throttle body. If you split the intake into 2 plenums with 36mm throttle bodies, then each cylinder is being fed by a 36mm throttle body. That will probably result in even worse breathing than the stock intake.
With that said, there are some ways to get around that. For example, if you put a "crossover pipe" between the plenums, that might flow enough air to make up for the smaller throttle bodies.
Another novel idea is to use a TPI V8 throttle body (they come stock with twin 48mm throttle plates), and make a V-shaped adapter to send the air from the two throttle plates to the two plenums. The advantage of that setup would be that you won't have to make a throttle linkage to connect two separate throttle bodies, or figure out how to make stuff like idle and TPS work.
Just a thought.
[This message has been edited by Blacktree (edited 10-01-2016).]
Been there, done that...once the novelty wore off, it was not worth it because of the weird throttle characteristics. It was almost like an on/off switch instead of a progressive, linear response. The dual throttle body intake made more power (according to the g-tech), but it was harder to modulate the throttle. Using a modified F-body 3.4 intake gave the nearly the same performance gain with only 1 throttle body and no ill effects.
I suspect its jubilance at attaining freedom was rather short-lived. Heh heh...
It sure was... Conveniently enough, it happened 1/4 mile from the junkyard So I just put it in neutral, pushed it there, they gave me $150 for it and I called my brother to give me a ride home
I know of someone who has already done this. Check the Georgia Fiero Club web site for pics.Look in the tech section, do a search for dual throttle body and go to the 2nd page of that thread. In talking to the owner , he runs 1 tps on 1 throttle body and 1 IAC on the other. Yes, it has been reprogrammed for the extra air flow. He also reports that it doesn't die out at higher RPM.
[This message has been edited by ron768 (edited 10-03-2016).]
Originally posted by Blacktree: Another novel idea is to use a TPI V8 throttle body (they come stock with twin 48mm throttle plates), and make a V-shaped adapter to send the air from the two throttle plates to the two plenums. The advantage of that setup would be that you won't have to make a throttle linkage to connect two separate throttle bodies, or figure out how to make stuff like idle and TPS work.
Just a thought.
Or, just swap to the 7730 ECM, switch to DIS, and install the F-body 3.4 upper/middle intake.
The ECM uses the TPS to know if the throttle is closed or if it moves open quickly and an "accelerator pump shot" of additional fuel is needed. The ECM doesn't use the TPS to determine how much air is flowing. It mainly uses the MAP sensor to determine how much fuel to inject.
I believe that the TPS % reading is taken into accord as part of the fueling mixture parameter. Even if that statement is incorrect dual throttle bodies will let in more air faster than the TPS voltage will indicate. You will be opening a throttle bodies at twice the flow rate as the one. Now if boot uses two throttle bodies that equal the flow rate of one then all should balance out but will the engine make more power?
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Originally posted by Dennis LaGrua: I believe that the TPS % reading is taken into accord as part of the fueling mixture parameter. Even if that statement is incorrect dual throttle bodies will let in more air faster than the TPS voltage will indicate. You will be opening a throttle bodies at twice the flow rate as the one. Now if boot uses two throttle bodies that equal the flow rate of one then all should balance out but will the engine make more power?
Not exactly. The TPS reading is an indication of load, when compared to other sensor data like IAT and MAP. With two throttle bodies, you can still have one TPS used, and it simply indicates the throttle position as normal. There's nothing to "balance" there. However, by splitting the banks to two independent intake air charges, one needs to balance the pressure across both plenums, to get the correct MAP reading. The EGR also needs to have a split port behind both throttle bodies, to balance the recirculation charge at cruise.
Without appropriate other changes though, to enable the engine to avoid valve float and actually reach high RPM, you'll probably not see much benefit. You'll likely end up with less low end torque, and maybe a couple more HP around 5200.
The ECM uses the TPS to know if the throttle is closed or if it moves open quickly and an "accelerator pump shot" of additional fuel is needed. The ECM doesn't use the TPS to determine how much air is flowing. It mainly uses the MAP sensor to determine how much fuel to inject.
Now I probably shouldnt be ghettocharging my daily. But Im still itching for a performance boost of some sort. So I thought, why not take the manifold I started making, and convert it to twin throttle bodies, sort of like a lambo?
So I just put it in neutral, pushed it there, they gave me $150 for it and I called my brother to give me a ride home 
