I'd go with the "race" if it has provisions for progressive or 1:1. Everything Monte said is true about the 1:1, but some engines are hard to drive with 1:1 linkage. The engine's reaction to throttle movement, if tuned well, is instant. The slightest movement of the pedal can give you more than you want, and setting the tps rate of change needs more sensitivity. All can be overcome, but the option is there if you need it.
I fix a lot of driveability issues AFTER tuners get there hands on cars, and progressive linkage always will be easier to drive.
If this is a car that is typically street driven, you would be much happier with this option, whether you use it or not.

Hi Trendz,

The car will have dual quads, so yes, I would want progressive linkage. It is a 604 Hemi that will be street driven, but not a cruiser, only a blast around town with a trip to the track once or twice a year.

The Black 112-602 race has the "Dedicated race only throttle lever" and from the pictures, the throttle lever is much different than the 112-587 universal throttle body, and the latter looks to have more sensor inputs???

I did talk with Holley today (finally called back) and they told me to buy the Holly EFI Digital dash (553-106) that replaces the 5.7" (553-103), but like Monte and Mike said, I will really need a PC laptop for the initial program load.

All this EFI stuff is new to me, so there is quite a learning curve.

BR, Mark

For whats its worth I have the cast EFI throttle body with the progressive linkage I am happy with it. It seemed to be the best value for a throttle body.

Its funny the cost of the holley EFI is what drove me to do a Megasquirt setup in the first place, but the holley throttle body was the best deal out there haha.

To me and most companies I might add, TBI is something for the average guy, who takes the carb off his streeter and wants an easy drop on EFI replacement. Not many fit that bill with a Dominator flange. Most want TBI to LOOK like a carb. Now as I said earlier, we are in development of a billet throttle body with a 4500 flange that will sit on top of a billet plate that holds 8 injectors that will be on an angle and spray down in the plenum. But those are our only plans on anything resembling TBI with a Dominator flange.

As for the 1200hp version of the 4150, I assume you are referring to the Sniper. It already has 8 injectors in that fully contained unit. There is room for no more, nor is there a larger injector that fits within those confines, so the throttle body is supplying all the fuel it can. One for a 4500 would have to be totally redesigned and if it looked the same, it still couldn't support more power because of the injector limits.........so whats the point.

Because you need one and don't want to run an adapter, doesn't make it feasible for us to build it. That would be a low sales product

The 112-587, 112-588 and 112-602 throttle bodies are identical other than linkage. The first two are progressive and have provisions for a Ford kickdown cable or a 700R4 cable. If you don't have these trans, it's a non issue. The 602 or RACE throttle body has the same amount of sensors as the other two and has the external linkage that can be positioned either way. It also only has 2 external vacuum ports, the others have 4, although the bosses are there and you could tap them if needed. So if you don't have a Ford or 700R4 tranny, it makes no sense to NOT get the 112-602 throttle body.

On a personal note, two throttle bodies or not, I would still run them 1:1

When I read that Jeg's comment I was in shock. I have sold and supported many systems over the years, and the Holley products are near the top I have supported, and certainly the easiest to get running. I used to joke that "learning systems" would put me out of the tuning business, but I'm busier now than ever because of all the weird combos people are putting together.

Thank you Monte, Rich, Mike & all,

I now feel a little more educated on this EFI technology!


Best Regards, Mark

Thats true...people like me putting small LSA cams in
EFI engines.. yes it works but it doesnt like it on
the self learn portion... its better now but the overlap
has its problems.... a 105 lsa is a bit much ... its got
so much over lap it has a hard time knowing if it should
add fuel or take it out.... yes I am learning I can pull
fuel out at idle to cover for it... but that will change
in a couple of weeks when I change cams