EFI heavy throttle/ spring load

Hi Anders,

I am not sure I completely understand your setup but I will say that it is a very good idea to have return springs at the throttles to ensure positive throttle control. Most sanctioning bodies require them (for non drive-by-wire) and for good reason. The are your end of line safeguard. Many good quality throttle bodies have built in springs.

Have you checked your throttle cable? They can add resistance.

Most multi throttle body systems I can remember had some sort of spring for the throttle body(s) and a spring (or springs) at the bell crank or at the end of the cable. The intermediate linkage(s) have a little adjustment so throttles can be sync'd and to be able to adjust the idle.

Thanks for your reply and ideas. Yeas, the throttle cable is all fine.

Anders

Anders,

Why did you switch from IPSCO's low profile ITBs to your old TWMs ?

Just curious.

David,

The reason is that with TWM´s you can adjust each runner individually. That´s why I make this change.

/Anders

Anders,

Do you find the TWM ITB's make a difference? I also have IPSCO ITB's and found that some of the butterflies had to be carefully smoothed around the edges to keep them from sticking in the throttle bores. Other than that, I've had no problems with them.

David,

No, the engine has never been on a dyno so for performance, no. I have not have any problems with the IPSCO´s other than that is trickier to set them up compared to the TWM´s and synchronize individually.

/Anders

I wasn't aware Mark made ITB's and I can't find them on his website. I'm looking at a custom application on a Toyota 2GRFE build.

He used to make ITB's but doesn't any more. He made the ITB's for Kelly Coffield's EFI packages that were based on Kelly's IR intake manifolds. That's how I got a set. I've also found that Mark makes lots of things that aren't on his web-site.

If you need EFI parts, check out  https://www.efihardware.com/ in Australia.

There should be no difference in feel from one system to the other.

Since it is likely that you had much of the throttle disassembled, there might be an issue with the way you reassembled it.

I have a Moroso double return spring installed to the bellcrank arm which is mounted to the center tower of the Weber manifold.

I initially had issues with the weight of the tension on the accelerator. I am using the original Pantera throttle cable.

What I discovered was that in that cable assembly, on the carburetor end is a metal tube that is used for the internal spring to ride over.

If that tube gets bent or deformed in any way, it causes increased effort on the accelerator.

I removed the tube from the cable assembly and now have a very light feel to the pedal. I would and have recommended the tube removal to anyone who asks. It likely is the source of the issue in many cases and really is not a necessary or critical component to proper operation. It just causes trouble.

Also in reassembling the throttle arms to the TB's, the linkage must be at 180°, neutral and not over centered.

You do not want to add additional throttle springs if possible. Regardless of if you are using Weber 48 IDA's or EFI TB's, the throttle shafts will wear prematurely if significant spring tension is added to the throttle assembly.

Anders, if your ECU supports it, you could always do away with your throttle cable and convert to drive-by-wire. It opens up a whole new world of tuning possibilities. I have a Holley Dominator ECU and a Jenvey Dynamics (UK) DBW unit. I used a Lokar DBW pedal but there are OEM pedals that work just as well.

A follow up...

Thank you for your advice.

David, you have a Nice throtle set up. The ecu I use is not  compatible with dbw. By the way, saw your short video on You Tube ).

I Will rebuild the throttle linkage, pictures later on.

Anders

A follow up...

I start all over from scratch. Panteradoug, thank you for your advice.

I made a new bracket, steady as... and bolted on a brand new bellcrank meassured to the center between the throttle bodies and a new wire. It's a Dream to drive now.

Do it right from the begining...

Happy driving to you all

Anders

Great to hear that you got it sorted and to your liking.

@sf posted:

A follow up...

I start all over from scratch. Panteradoug, thank you for your advice.

I made a new bracket, steady as... and bolted on a brand new bellcrank meassured to the center between the throttle bodies and a new wire. It's a Dream to drive now.

Do it right from the begining...

Happy driving to you all

Anders

Yep. It isn't rocket science, it is just different from what you have seen before.

Once you understand this type of multiple carb/throttle body linkage you will be good forever.

On the Pantera, that center tower pivot is very important AND there is a degree of incompatibility to the original cable throttle that needs to be modified.

The "tower" makes it "easy" to run the left and right side throttles opposite to each other with little or no change to hot idle rpm because of heat expansion on the linkages with a light feel to the throttle pedal.

Considering that all was intended to maximize the potential of the intake as a race design, it is a very sophisticated idea most often overlooked as poppycock by  self proclaimed nouveau experts, which it definitely is not.