Single Throttle Body Setup Question Options

[Craigers17]

This thread is meant to "sort of" piggy back off the current thread on fuel delivery setup options. I see that Clay has this link for a complete modern EFI system:

https://store.allzim.com/914-parts/fuel-del...efi-conversion/

...and I know the Dub Shop has a similar setup. I also see that the Dub Shop has both a single throttle body & a turbo plenum single throttle body setup. Here:

https://thedubshop.com/single-throttle-body-intake-package/

and...here: https://thedubshop.com/single-throttle-body...-turbo-plenums/

Sooooo....since I'm not the sharpest knife in the drawer, can someone educate my dumb ass on why it seems much harder to develop an aftermarket single throttle body setup for a Type4 / 914 engine as opposed to a Type 1? Or maybe I should say as opposed to one with a Type 1 shroud. It seems like the air and fuel travel the same distance. What am I missing? I do realize that 2-3 companies are working on this....just wondered why it seems to be more of a challenge.

[GregAmy]

...can someone educate my dumb ass on why it seems much harder to develop an aftermarket single throttle body setup for a Type4 / 914 engine as opposed to a Type 1?

It's not. It's just that Mario's (Dub Shop) market for Type 1 stuff is very much larger than for our Type 4 stuff. And that's what Mario does for a living.

See my sig for a link to how to do it yourself using D-Jet components. That was my COVID project to keep me sane...maybe someone is willing to run with it and sell it retail, the details are all there (send me a six-pack of your fav local IPA).

[ClayPerrine]

This thread is meant to "sort of" piggy back off the current thread on fuel delivery setup options. I see that Clay has this link for a complete modern EFI system:

https://store.allzim.com/914-parts/fuel-del...efi-conversion/

...and I know the Dub Shop has a similar setup. I also see that the Dub Shop has both a single throttle body & a turbo plenum single throttle body setup. Here:

https://thedubshop.com/single-throttle-body-intake-package/

and...here: https://thedubshop.com/single-throttle-body...-turbo-plenums/

Sooooo....since I'm not the sharpest knife in the drawer, can someone educate my dumb ass on why it seems much harder to develop an aftermarket single throttle body setup for a Type4 / 914 engine as opposed to a Type 1? Or maybe I should say as opposed to one with a Type 1 shroud. It seems like the air and fuel travel the same distance. What am I missing? I do realize that 2-3 companies are working on this....just wondered why it seems to be more of a challenge.

I have talked with Aaron @zims ( @Partsguy22 ) and while it would be easy to setup an aftermarket EFI system that used the stock 2.0 intake plenum, throttle body, and air cleaner, it has two disadvantages. 1. The throttle body is a restriction in the intake, and 2. it would require completely different programming. Most people that put aftermarket EFI on their cars want the extra performance.

Granted, you could put a new plenum on with a larger throttle body, but you are still faced with the same pressure drop issues at low RPMs that are resolved by multiple throttle bodies. Smaller runners increase air velocity at low RPMs, increasing performance. But a single small throttle body restricts air at high RPMs. That's the reason that car manufacturers used 4 barrel carbs instead of just one giant barrel.

Now if someone wants a "Stealth" EFI system that looks like a factory system, it can be done. But it would require some lateral thinking on how to hide all the "modern" components.

[914werke]

I'm not sure I agree with your summation.
Many seeking such a solution aren't necessarily looking for more
Performance but I'd hazard more reliability.
On a stockish engine you certainly wont get more but you wont see
Less performance with a system based on the OE induction pieces.

[rfinegan]

IIRC: Jake and Mario are working on a Single TB Type 4 modern injection system....

[GregAmy]

...it has two disadvantages. 1. The throttle body is a restriction in the intake, and 2. it would require completely different programming. Most people that put aftermarket EFI on their cars want the extra performance.

I'll also disagree with the "most" word.

First, on throttle body airflow. My D-Jet conversion, on a dead stock engine, was 96 horsepower at 2900 and 88 torques at 4400, with the torque flat to just over 5200. This is at the hubs on a Dynapack.

But more importantly, my MAP is usually in the 98 kPA range at WOT and 6,000 RPM in the plenum. If I'm reading the data correctly then that mean I'm roughly 97% or so of atmospheric in the plenum of the D-Jet system. That implies the stock throttle body isn't much of a restriction.

Now, the runners will no doubt offer some additional restriction. And the throats are not pointing right down into the cylinders. So, yes, someone building up an engine with cams, compression, and porting will certainly want more airflow than what D-Jet will provide. But I offer that on a mostly-stock engine the D-Jet induction system is surprisingly good for the application.

I actually bought throttle bodies and all required components from Mario to convert my D-Jet system to ITBs: https://thedubshop.com/dual-idf-throttle-bo...injectors-vwss/

I had everything I needed to install it, short of motivation and some electrical pigtail adapters. I ended up selling all the components to a member here because while I would have liked to have pursued it for the knowledge, on a mostly-stock engine I just wasn't going to get much out of it.

It would have been nice add to my historics race car (high compression, big valves, porting, 86B cam) but that's running fine in dual Dells so I'm not gonna fark with it.

As for "completely different programming"...that concern I don't get. Different from D-Jet? Of course it is. But it would be that way with any other system, even carbs (jet tuning is an analog art all by itself). There is a learning curve for anyone that was customized programming (or carbs); in fact, everyone would have to learn how to do it themselves because every one of their engines would probably be differently built and a supplier cannot account for that (D-Jet was designed for a single build spec).

As I noted in my opening monologue in the blog, the D-Jet system is pretty damned remarkable for something that was designed over half a century ago; I think we are now all beginning to believe that. And if we could continue to get replacements parts at low costs for it, then I see no reason to move away from it on a stock engine.

But with components becoming scarce and spendy, and a desire for moar powah engine components, a modern interpretation is warranted. I'm delighted we have several options now.

- GA

[Craigers17]

I appreciate all of the feedback and information. @GregAmy I read your entire MicroSquirt document....very informative and I'm sure there are many, including myself, that are very appreciative of your documentation.

I agree that to many of us the stock D-Jet is a pretty good system from the get go. My problem is that, while I could probably scrounge up a pair of runners from what I have, I'd have to buy the plenum and throttle body at the very least to go the Microsquirt route or to go back to D-Jet. More than likely the throttle body would then need to be refurbished.

At the same time, I really prefer a single throttle body vs going dual anything. Personally, I'd rather have the reliability and simplicity over increased power. When you have dual carbs or ITB's, you still have to have dial in 2 different mechanisms and then get them sync'd together. Not only that, in the case of carbs, you have 2 different units that can get jets clogged, etc. I would like to combine something like Microsquirt with a similar to stock, yet modern throttle body with modern runners and EFI, similar to Mario's Type 1 system that I linked in the first post.

I'm really just trying to educate myself so that I am at least aware of the best options out there as I start my next driveline setup. My current engine is toast, so I'm at a crossroads as to which direction to go. My next step is going to be dropping the engine and doing some analysis. Then we'll go from there.

[VaccaRabite]

Like Greg, I also put together a single throttle body Microsquirt EFI based on 1.8 Ljet parts. On a 2056 it made a lot of power, and I spent a lot of time tuning and tweaking it. Which was fun. By the time I replaced it with my current 2.3, I had it running really really strong. It ran like a top, was super fun, and I would 100% NOT do it this way again.

My current engine is using independent throttle bodies on Terminator X. And its awesome, but really complex. Simple stuff like idle control - well it isn't simple with ITBs.

For my bus, I am looking really hard at the Holley Sniper TBI set up. Single throttle body. Self contained (mostly). All you need is a T4 manifold (pretty much the same one you would use for a single carb system) and send it. Its a way simple system without all the extra wires and hoses.

Of course, its not that easy. But after playing with ITBs it will feel that way.

Whatever way yo go, there are some things you are going to need. You are going to need a wide band O2 reader. You are going to need some way to do spark control - and everything is better then a dizzy. Everything on the market these days can do spark control, and its so much better. Mario sells a very good crank fire set up for the T4, though you have to drop the engine to install it, and you want it RIGHT before you put the engine back in.

Zach

[GregAmy]

Mario sells a very good crank fire set up for the T4, though you have to drop the engine to install it, and you want it RIGHT before you put the engine back in.

I'm using his CPS setup on mine, works great...but it requires removing the engine to get to the front.

But...if you're not stuck on sequential injection and ignition (and I'm not, see discussion here halfway down) then Mario is about to produce a 24-2 wasted spark "Mini Cam Sync" that replaces the disty and is driven by the cam:

https://thedubshop.com/mini-cam-sync-v2/

I've not tried it but I'm likely to, once he gets rockin' on production. And it should be a plug-n-play install for my setup. And no engine removal required.

[914werke]

I also put together a single throttle body Microsquirt EFI based on 1.8 Ljet parts. and I would 100% NOT do it this way again.

@VaccaRabite
Zach I was unaware that endeavor was using the L-jet AFM ?
Id like to hear more in depth about it. Perhaps I missed it?
Lastly what specifically was the challenge that you would dissuade other from that route?

[VaccaRabite]

I also put together a single throttle body Microsquirt EFI based on 1.8 Ljet parts. and I would 100% NOT do it this way again.

@VaccaRabite
Zach I was unaware that endeavor was using the L-jet AFM ?
Id like to hear more in depth about it. Perhaps I missed it?
Lastly what specifically was the challenge that you would dissuade other from that route?

Yes!

So I did not use the AFM - or any of the L-jet sensors. In fact I removed the barn door/flapper and made a custom tube from the air filter housing to the throttle body housing. I could have sworn I had pictures of this, but now I can't find them.

But long story short, I swapped out or eliminated all the 1.8 sensors and replaced them with modern stuff. The TPS I used fit exactly right without mods. I did not use the ljet AFM.

Why would I not do it again? Oh, I would. I would just not use Microsquirt to run the show. The tech has moved forward. The Terminator X does a LOT of self learning once you get a solid base tune. Same with the Sniper. When I did Microsquirt, this was kind of the wild west, and I had a steep learning curve. The tuning took about a year to get it where I liked it, and using old parts had all the issues of using old parts. Worn out throttle bodies. Cracked plemun. Finding or modding parts that could be worked to fit while keeping a stock outward presentation.

I've not used the Sniper yet, and I want to which Is why I'm thinking about it for my bus. And I think its probably the easiest of all the current options out there.

Zach