Bigger M104.980 throttle body?

[John5788]

I'm going to be doing some modifications on the throttle body for my CIS M104 motor. Does anyone know if there are any larger throttle bodies that directly bolt on? I'd like to start my little project on the bigger throttle body if such a thing exists off a different engine or something.

Do the standard M103 throttle bodies, say off a 300E, also fit? Same diameter?

[Frank Reiner]

Bigger than....?
Recently, some folks have resorted to the use of numbers to help with the idea of "bigger".

[John5788]

I'm still in the initial stages of just scoping out the work to modify the throttle body for running a TPS that has both a potentiometer and microswitch. So I don't have any concrete numbers to go with at the moment. Just by searching around I'm gathering that the stock bore is probably 70mm, but that number was for the M104 HFM motors with the electronic throttle, not the older CIS style. So something wider than 70mm? Anyone know if the V8 CIS throttle bodies fit?

If the M104.980 TB is as big as it gets for that intake manifold, then I'll just continue my work on finding a scrap unit to take apart and modify. But if there's something bigger and better for me to start with, I'll source one of those instead.

[duxthe1]

It is a 70mm throttle body on the CIS motor. When I modded a stock 60mm 103 T/B to 70mm there was very little meat left in the flange to seal it to the manifold. The 104 part isn't much better. When I put EFI on my 103 I had to make a spacer for the TB because the TPS sensor hit the manifold. The throttle shaft is very close to the flange so there isn't much room for a sensor without spacing it up a bit.

[John5788]

Originally Posted by duxthe1

It is a 70mm throttle body on the CIS motor. When I modded a stock 60mm 103 T/B to 70mm there was very little meat left in the flange to seal it to the manifold. The 104 part isn't much better. When I put EFI on my 103 I had to make a spacer for the TB because the TPS sensor hit the manifold. The throttle shaft is very close to the flange so there isn't much room for a sensor without spacing it up a bit.

What kind of TPS did you use and how tall was the spacer? I have a feeling what I had in mind won't fit if the spacing is so tight. The Z32 300ZX TPS looks very rectangular and might be too wide to fit.

[duxthe1]

I used a BMW sensor but don't recall the specific model I pilfered it from. Had to make an adaptor that would allow the MB shaft to drive the sensor. Its been a while but I feel like it needed about half an inch but I made an inch tall spacer to have some wiggle room.

[97 SL320]

A larger throttle body might make the car "feel" faster at low speed but it really isn't. The down side is the car can be difficult to drive at parking speeds.

Since a larger throttle body will flow more air per degree of opening, 10% throttle peddle will equal more air over 10% of the smaller one.

This is similar to the round throttle cam sold to hop up a Porsche 924 / 944. All the round cam did was change pedal to throttle blade ratio making the car feel faster.

Late 90's GM Vortec V6 / V8 engines used a single very large throttle body but added a slab to one end of the throttle blade in order to prevent jumpy throttle response at low speed.

See 2:20 4:10

Published on Mar 21, 2012

Easy free way to gain a noticeably better throttle response. Does not gain horsepower like companies claim. Please read description. Thanks.

https://www.youtube.com/watch?v=okEDVwlEHvM


The only way a larger throttle body helps is at high speed " if " it is posing a restriction. If you are not maxing out the stock TB, you will see no gain other than a perceived low speed increase.

[Justin300sl]

What are your plans for the vehicle? Getting rid of cis? Sounds like it if your trying to add tps.

Not knowing your plans with car I'll tell you what I'm doing on my turbo 980. I bought a weld on throttle body flange for early 90s 5.0 mustang, it's used for making your own manifold on the 5.0, and a 5.0 throttle body. I went with a 75mm, and that's about absolute max needed for the 3.0 turbo.

Unless your going huge turbo/blower, 70mm will be plenty for this engine.

The hole under throttle body is in our manifold is just over 72mm

I went with that throttle body because it is cheap, tons of cheap TPS and idle air valves out there for it, and I can clock the flange how I want it before welding on.

Good luck

[John5788]

Originally Posted by Justin300sl

What are your plans for the vehicle? Getting rid of cis? Sounds like it if your trying to add tps.

Not knowing your plans with car I'll tell you what I'm doing on my turbo 980. I bought a weld on throttle body flange for early 90s 5.0 mustang, it's used for making your own manifold on the 5.0, and a 5.0 throttle body. I went with a 75mm, and that's about absolute max needed for the 3.0 turbo.

Unless your going huge turbo/blower, 70mm will be plenty for this engine.

The hole under throttle body is in our manifold is just over 72mm

I went with that throttle body because it is cheap, tons of cheap TPS and idle air valves out there for it, and I can clock the flange how I want it before welding on.

Good luck

Correct, I am trying to add a TPS while keeping the stock fuel management system happy. I'm not getting rid of CIS, but I have full control of my AFR through a Microsquirt

I'm having problems with the trying to use purely a map sensor for decel fuel cut off events. My parameters for cutting fuel is currently defined as >1500 RPM and MAP < 20 kPa. This works when I'm moving and in gear. But unfortunately in neutral attempting a launch triggers the same criteria and I get a fuel cut.

My solution is to get a TPS with both a potentiometer and a microswitch. I'll feed the variable 5V signal back to the Micorsquirt and the microswitch for idle/WOT will go back to the stock CIS computer on the 3 terminals located on the intake manifold.

[whipplem104]

Just share the idle contact switch signal for both. You can share the signal between two computers.

[Rital24]

Your M104 has 70mm throttle body, M103 has 60mm.
M119 has a bigger TB but You need to make some modification I suppose.
Do You want to super/turbo charge your engine?