Fuel Economy vs. HP, Then & Now

[CaliWagon83]

So just for $#!+s and giggles, I looked up the EPA ratings for the '84 Regal with the 3.8L 2-bbl engine (the furthest back the EPA site goes is 1984), and '87 GN/GNX compared to the Cadillac ATS-V and CTS V-Sport. As you're probably aware by now, I have a slight fetish for those Caddy twin-turbo V-6s, and it's still my goal to swap one in.

At any rate, I thought it was interesting that all of the engines get about the same fuel economy. They're similar displacement, but the Caddy mills have approximately quadruple the HP of the NA 3.8. So it'll be about a wash from a fuel economy standpoint, but I'll be getting a lot more power. Seems fair.

FE Comparo Cadillac ATS-V, CTS V-Sport, '84 Regal 3.8 NA and '87 GN/GNX

• CaliWagon83
• Dec 31, 2017

Fuel Economy Comparison, Cadillac ATS-V, CTS V-Sport, '84 Regal 3.8 NA and '87 GN/GNX

 

[pontiacgp]

That is interesting, the largest gain in the fuel economy with the added HP is in the transmission...

 

[CaliWagon83]

Yeah, a big gain is probably going from a slippy 3-speed to a tight 8-speed.

 

[Turbolq4]

Would be really cool to see one of those twin turbo v6s in a Gbody!! I'm a fan of them as well. Pretty much a fan of turbo anything.

 

[CaliWagon83]

Turbolq4, I haven't given up on my dream of swapping one into the CaliWagon. Got a lead on an engine+trans combo in San Diego for $6k. Just a hair over 22k miles on it. I told the yard I was interested in it, or any other LF3 or LF4s that come through.

 

[Turbolq4]

Engine management would have me a little anxious. Not sure if you can tune them or what options are available. Would be awesome to keep factory driving characteristics just in an older car.

 

[CaliWagon83]

Engine management would have me a little anxious. Not sure if you can tune them or what options are available. Would be awesome to keep factory driving characteristics just in an older car.

I would only take it if the ECU and TCU were included. Being in CA, I think I'd probably just keep a stock tune. I don't know if there are any smog-legal tunes available for it. But at between 420-464 hp and 430-445 lb-ft, I think I'd be happy. 😎

 

[jiho]

The problem is that this motor (or any 1996-up motor) has a gas tank pressure sensor, and the computer will throw a code if the sensor is missing. And California (according to Clone Pilot on this site) prohibits all three ways of dealing with it: 1) reprogramming the computer to ignore it; 2) adding the sensor to your G-body gas tank; 3) installing a non-G-body gas tank that has one.

I haven't called the Bureau of Auto Repair myself to verify this, but I have checked the rules and guidelines, and it does indeed appear to be the case. Your smog-legal options are basically confined to any factory-stock motor 1995 or earlier, that is also the same year as your car or later.

 

[CaliWagon83]

The CA engine change guidelines are both ridiculously restrictive and frustratingly vague and subjective. From a few other forums I’ve read, from the sound of it, if you bring your car in to a ref facility, as long as you have pretty extensive paperwork, it doesn’t throw codes or CELs, and isn’t producing excessive emissions, they’ll usually pass you, or at least give you a “fix it” list to get a pass.

What would be ideal would be to get a full donor salvage vehicle for all the little, obscure parts to make everything work right.

A good test-case for this would be any non-E-Rod LS swap in CA. If anyone’s had this done, and has gone through the whole BAR ref process, would like to hear about the experience and potential pitfalls and unexpected headaches.

 

[fleming442]

Personally, I want to see it; make it happen, now!
AS far as tank pressure, just put the sensor and purge in line to the EVAP solenoid on the tank vent line. I'm fairly confident that will work.