You guys ever notice the throttle arm on the y-body vs f-body has a different ratio?

I measured it, and the vette has about 1" of travel, vs almost 2" for the fbody version.

I'm guessing that translates to more aggressive throttle response on the vette?

Anyone ever run an fbody throttle body on their LT1 car?

-- Joe

 

I don't believe that's so. The throttle-body I believe is the same but the application changes the linkage. Corvettes all have ASR and the F-body, B & D bodies don't so there's changes that are accomplished with various changes.

 

I have also seen a more aggressive curvature on the brackets, especially on the aftermarket throttle bodies. It definitely effects the rate the butterflies open relative to the distance of travel of your foot, which increases throttle response just as you said. Sometimes it can be too touchy in my opinion with the aftermarket setups.

 

I spent a couple hours researching this. Regarding stock throttle bodies, the y-body has a different part number than the f-body. I also checked the aftermarket, and they typically include different ratio arms for the various applications as well.

I deleted the ASR on my C4 and used a fbody throttle cable, which had to be shortened by about an inch. I didn't understand why the cable was too long since the fbody also uses an LT1, until I had both new fbody and ybody throttle bodies in my shop and noticed the travel on the fbody unit is twice as far for the same throttle opening.

It's interesting. If I had a lokar adjustable cable I'd probably try both, but changing cables sucks on these cars (about an hour). Either you have to drop the column or remove the seat and lay on your back.

Another member pointed out on the thirdgen forum that the ybody throttle body is a little too sensitive with his 4.11 gear ratio. I started thinking, and most of the ybody have 2.59:1 or 3.07:1 gear ratios, whereas the fbodys were 3.42:1, 3.73:1. I wonder if the ybody got a more aggressive throttle body ratio to compensate for the lame rear end ratio?? Food for thought.

I have a 3.07:1 rear in my '94, but even so I bet the fbody throttle body would feel lazy. I just found the differences interesting.

-- Joe

 

Nah, they are way different. I'll post pictures later.

I don't think the ASR has anything to do with it as that's an independent component. I think it's more likely they wanted to alter the throttle response vs pedal travel due to differences in the final drive (gear) ratio.

It would be great to be able to spend a day talking to one of the design engineers.

-- Joe

 

The ASR is "in series" with the throttle cable. There is a cable from the pedal to the cable adjuster, and then a separate cable from the adjuster to the TB. There is also a cable from the adjuster to the cruise control unit. Now, as far as I can see they are all on concentric cams with the same radius, so no change in ratio there. But the ASR is definitely smack dab in the middle of the throttle linkage.

 

I realize that, I removed mine last week when I went to the fbody cable.

But the ASR doesn't change amount of cable draw vs pedal movement, so my point was that the throttle body arm ratio difference has to be related to something else. The most likely thing I can think of is the rear end ratio.

-- Joe

 

This discussion is of interest to me as I had been thinking of posting about a similar observation I've made, regarding the pulley/arm ratio of the LT1 TB.

It has a cam that requires a great deal of throttle pedal movement initially, to get a significant change in angle of the plates. I'd assumed that was to reduce throttle "tip in" sensitivity. IDK. Anyway, the last bit of throttle pedal/cable travel and you hit the smaller radius of the pulley/arm and you get a dramatic angle change per unit of cable movement.

I was going to ask if anyone had used a L98 TB which has a continuous ratio throttle arm/cam, on an LT1 and what the effect to drivability was (throttle sensitivity).

It seems that Anesthes is asking about this w/regard to fitment, I'm curious about it from a drivability stand point, but I'd bet that both of use are asking a question that has to do w/that cam'ed throttle arm...although it looks to me like the F-bod has the same arm. (?)

 

I sold an F-Body TB to a member on here last week. After reading what Anesthes found with the cable length differences I wonder if he was able to make it work. I will send him a link to this thread.

 

I was curious about both fitment and function. GM obviously changed the arm/cam/whatever for a reason on the ybody application. The caprice/impala seems to use the same throttle body as the fbody.

I meant to take pictures of these side by side for those who have not seen both, but I've just been really busy. Maybe tonight.

-- Joe

 

i put in on and it seems to work fine. Tonight I will compare the linkage on it to the original one I took off and let you know

Mike

 

Is the pedal lever arm length on the cable the same in a Y-body as the other LT-engine cars? It isn't hard to imagine that the limited space inside a C4 made it impossible to use the off-the-shelf pedal assembly that GM used in a bunch of other cars.

 

That is a very valid point. That foot well isn't spacious!

 

You sold "mlm0" an LT1 TB or maybe a L98 TB? I believe he's an '89 L98 so his observations can't be used as a direct comparison.

As far as the LT1 to LT1 comparison I'd think in addition to the ASR/TV control function it's also directly related to the pedal lever ratio "in the car" at the pedal as mentioned by "MathewMiller". I'd think regarding the OP's observations it only establishes that with substantial modification you can "maybe" make nearly any combination of components work. OP needed to or elected to remove the ASR function and then elected to use an F-body cable that needed further modification to function to "his acceptable" function.

Ain't no way! WOT is directly related to the "pedal ratio''(in car) and the TB lever ratio at the TB.


***It appears that the actual pedal changed in '92 so it would be likely safe to assume that there was actually a ratio adjustment.

 

The 85-91 cars used the same TPI throttle body/arm as the fbody platform, and the pedal in the vehicle worked just fine. I don't think it's related to the ASR as the ASR does not appear to effect the ratio at all.

WOT is irrelevant, it's the initial throttle response and amount of travel to get into AE. All the way open is all the way open, but if the pedal movement is much less to get the car rolling it will feel faster, even if it has a lazy rear end ratio (which all C4's have).

All the replacement/reproduction accelerator pedal assemblies list 84-96. Are you sure 92+ is actually different?

-- Joe

 

An OE/GM pedal is #'d differently and I suspect there's a reason! Thru '88 there's a pedal that matches the cable applications, '89 - '91 a different pedal to match that different cable and then a '92+

I thought all TPI were an eye over a stud for cable control at the TB and all LT1 were "slug on a roller" like the Corvette. There were studs on the lever/TB control but those weren't intended for accelerator control. TV and cruise I'd think.

Camaro control: http://www.wholesalegmpartsonline.co...riveLine=11463

 

Early TPI was eyelit/stud, late TPI was barrel style.

All LT1 are barrel style.

Fbody and ybody TPI used the same year for year. The LT1's are where they seem to be carline specific throttle bodies.

As far as the pedal goes, I realize they might have different OEM numbers. I'm curious what the difference is.

-- Joe

 

F body



Original


i have included pictures of the TB now on the car that I think came from F body and pictures of the original one I took off. The part numbers on the throttle bodies themselves are the same. Different numbers on the linkages. The F body TB has a much sharper cam angle then the vette one. The vette one is a smoother radius with no sharp angle. I don't know how much pictures will help. I now wonder if this will effect my cars performance

 

Sorry, I was referencing L98s despite the title of the thread being LT1. The TB pictures he posted show the TB I sold him from an 89' Firebird; it is the one with the flat ground on the bottom of the cable guide.