TBI cams

[4X4HIGH]

try throwing TBI on a thumping hotrod motor cam with a low centerline and see if it'll run.....

Exactly my point. You install a cam with 102 lobe separation angle in a MAP EFI system and it's highly unlikely the engine will even run (not computer friendly).

 

[ryoken]

I'm sure the majority of that was covering their arses type thinking when it came about...

but I'm betting there was a bit of a "hey, we better let all these oldschool carb type guys know that they can't be running those same lopey cams with newer EFI motors" message in with it too.........

save themselves some tech headaches down the road...

 

[4X4HIGH]

Then why argue that there is such thing as a computer friendly cam? There isn't, that is a fact. If you HAVE to tune it to get everything out of it, then it's not really friendly with the computer.

"Computer friendly", at best, is misleading.

The ECM can only inject the amount of fuel it is programmed to inject (outside of mechanical limits of course). The "on" time of the injector is how it changes the amount of fuel added to the motor. If the valve stays open longer (or opens earlier, or closes later, whatever) the only way more fuel is added is if more fuel is available. The PROM has to be programmed to get that extra fuel in.

On a batch system you are right, there is more fuel available per cylinder because it's "shared" amongst four cylinders...but if you are pulling more for each cylinder, eventually the engine will pull more fuel than is required to keep from running lean, unless the PROM is programmed to give what the engine needs.

I'm not saying they don't make a difference. But if you are going to need to tune something to get all the benefit out of it, why limit yourself to "computer friendly" grinds? You can feel a lot more power in an engine, and still be lean. I suspect these cams are mild enough and GM was conservative enough that there is perhaps an overlap on how much fuel is injected under heavy throttle, but there is no way to know for sure without hooking it up and looking at the data. If it was a serious issue in all uses, these cams would be gone.

I use my Dad's 454 as an example, because it's a very mild motor...Edelbrock performer intake, mild cam, and headers. Fueling was 20% off (lean) from stock, not only 20% on the VE tables, but had to crank the fuel pressure up as far as the TBI pump would go. That's dangerous if undiscovered. It ran fine, you couldn't feel it or tell it any other way. But towing a trailer over the mountains? Someone who likes the throttle?

This is kind of like saying that if you buy a new carb for your engine it's not "engine friendly" since you still need to "tune" it. Hell lets take it even further and assume you buy a new distributor and just throw it in without "tuning" it either, guess that makes it not engine friendly either.

 

[dyeager535]

I can't recall ever seeing any manufacturer inference that you can simply slap their carb on a motor and have it run fine with no work, which is exactly opposite what manufacturers do by calling camshafts "computer friendly".

 

[shady]

all computer friendly is stating is that it will run.......

"I can't recall ever seeing any manufacturer inference that you can simply slap their carb on a motor and have it run fine with no work"

you answered your own argument right there