Possible to lower engine temp enough to safely run87 octane?

I was wondering if upgrading exhaust flow and adding cold air intake, an IC, and a 180* thermostat to a stock engine would lower the knock enough to run 87 octane safely. I know that it isn't terrible to run 87 octane if you accelerate like a grandpa, but is it possible to lower the knock enough that you can drive the car normal with 87 and not have any problems?

The performance of the car is fine for me as it's my daily driver, and I'm looking to do any mod I can that will increase fuel economy and possibly lower the octane required. The car has 153k miles on it and right now (with really bad front wheel bearings) I'm getting between 24 and 25 mpg driving around fairly conservatively ( with premium at about 12% more than regular). So, if I could get my octane down to 87 the price would be the equivalent of 26.88 to 28 mpg.

I know this is a performance riviera site, but IMO efficiency is performance, and raising fuel economy is causing the car to run more efficient.

This is very possible with a stock SC pulley and an IC. In fact, by adjusting timing, you can actually race on 87 if you do it correctly. Tuning is the key. If you're interested in ultimate economy, you'll want a tuner. I've heard of some getting 45 MPG out of these engines.

I agree, efficiency is performance! Also check out some of the threads on mileage mods and hypermiling techniques.

Just remove the supercharger belt!

Seriously, if you want to run 87 you'll have to massively modify the timing tables, reducing performance so much I doubt you'll be saving much in gas. Option II as AA stated - add an IC. A tuner is required to modify your timing tables.

I'd think investing in premium gas instead of a $600 tuner and $$$$ intercooler would make more sense. But it's your money, and it can be done if you want to invest the money and tuning time.

I have an intercooler off my 1987 Chrysler Conquest turbo parts car. Would that work with some minor retro fitting or would it be too small? The Conquest is a little 2.6 liter 4 cylinder.

I agree that spending that kinda money to be able to use 87 octane is kinda foolish, but I'll try searching around for the stuff I'd need and see about how much it'd cost.

What kind of IC is this? If it's air-to-air, you're faced with the problem of intercepting the air after the blower, before it gets to the lower intake manifold. It's been done, but man - what a plumbing job this would be. Lots of custom machined parts involved.

Our ICs are most always liquid cooled using a specially fitted core between the blower and LIM.

Oh, also, whenever my dad drives my car he puts 87 in it, because he doesn't think the 91's necessary. When I try explaining to him why it needs it he just brings up the DeTomaso Pantera he used to own that was blueprinted and balanced with a 10qt racing oil pan and a bunch of other goodies. It required 102 octane and if he only put in 91 or 93 octane it would sputter really bad on acceleration, but he never had reliability issues. He owned the car for 5 years. He keeps trying to tell me that it burns hotter so it keeps the engine clean and that's it. I try telling him that 87 octane will burn too soon (before spark) and that could be bad on the pistons, especially if it's way too early, like when the piston is all the way down.

It's like talking to a brick wall with him, lol.

The intercooler I have is liquid cooled. I guess many people that add turbos to their cars look to starquest owners for our intercoolers because they aren't that bad, and then the starquest owners look to other places for better ones, lol. I figure I have the extra one why not use it. I also have an extra oil cooler, but that would be a PITA to retrofit.

here's a pic of one

In that case, all you have to do is fit the core into the LIM. Might take some machining, but it's doable, imo. What does the core look like?

Conquests are cool. Look in the Racing and Kills forum for my race against one in the Riviera.

About the octane, using 87 isn't a guarantee that your engine will blow up, but it's not a good idea. It's like not brushing your teeth - you can get away with it for a while, but not a great idea long term. I have verified with a scan tool that KR levels do increase with lower octane gas. The knock is there, whether or not you think it will hurt your engine is up to you. I tend to side with caution and not run with knock, as sustaining this condition could lead to worse problems.

And about burning hot with 87 "cleaning" the engine... consider that many premium fuels also contain added detergents in addition to the extra octane, so you tend to have a cleaner engine using the good stuff. Shell V-Power is an example of such.

Keep running 87 and you WILL be replacing a piston with a hole in it. Search the forum for 'octane' and you'll find a long thread about it. Knocking like that will eventually kill the motor. As far as the IC goes, it all depends on the shape of the core. It has to fit between the SC and lower intake, which is not like a turbo - the SC is mounted directly on the lower intake so you can't really divert the air to an external heat exchanger unit.

The front radiator part looks okay since it was liquid cooled, that, a pump and a core is pretty much all you need.

Or for less than $500.00 you could try water methanol injection.
www.snowperformance.net/
This will allow you to run 87 octane and keep cylinder temps down and increase fuel mileage.

Check out their site for more info.

Regarding water injection, be aware that injecting upstream of the blower could cause damage to the epoxy coating on our rotors, lowering boost efficiency. I've seen a website claiming proof of this with before and after photos of the damage.

There's just no easy or inexpensive way, is there?

Take the supercharger belt off... seriously.

AA- the coatings of the Gen V rotors are different than the Gen III. A wet nitrous was a big "no no" for the gen III... now the Gen V seems to be impervous to nitrous, meth, etc...

Just another reason to upgrade to a Gen V.

deekster_caddy wrote:

Take the supercharger belt off... seriously.

Wouldn't I have to have the PCM rescanned if I took the sc pully off? since the car is supposed to send more fuel at higher rpms because of the sc, it would then be running rich without the extra air.

You are correct, Dustin. The car would not run optimal without the SC belt. In addition, the blower would now function as a restriction instead of a power adder, so efficiency would be compromised. However, running rich is preferable to running lean because you would not see any knock.

I think the deekster was half way pulling your leg!

yeah, i figured he was. yeah the reason running rich is better than lean is because the only thing you'll be doing is running more fuel through than can burn off, so you're more apt to foul plugs and ruin your cat, but that's a lot better than messing up internals. If the SC goes out, I might just take it off and swap out pcm's with an na 3800 series 2. Eventually I'd rebuild it, but that will be closer to the time when I put the engine in my fiero. Kinda wanna keep the riv though and just buy another series 2 3800

I am serious. If you remove the SC belt, your fuel trims will be off while it learns, but will settle in quickly to the new lack of air. It's not based on RPM, but airflow through the MAF. As long as your MAF is working properly, you should be okay because you simply won't be drawing enough air. You might want to lock the boost bypass valve open so you are always bypassing the SC. Then what you have is a low compression 3.8 which should handle 87 octane no problem. You'll save gas because you stay out of boost and use less air (and thus less fuel), plus you don't have the parasitic losses to spinning the supercharger all the time. Although, you'll also accelerate slower.

Is it optimal? No. Of course in an ideal you'd want to re-learn your VE, MAF and timing tables to optimize for 87 w/ no SC. I'm thinking about doing exactly that for the winter months....

You would not want to simply swap PCMs with an N/A car. They run higher compression, smaller injectors (I think) and have completely different fuel and timing tables to what you'd need to run.

okay, so it'd be a pita to swap it to na if my sc went out. Thanks for the info

So you bought the Riv to use the drivetrain in a Fiero swap? Cool. I helped a local friend with a Fiero swap recently, making the CV shafts up was the hardest part, but what a fun car to drive!!!

Yeah, i bought it as a daily driver for now, but when I get the rest of the money up for the swap that's where it's going. I'll probably put the 3.4" pulley on it and do a little more work to it before I put it in the fiero. Hoping to get into the low 13's or high 12's and still be reliable. If I end up liking the riv enough I might just buy an ecotec and put it in the fiero, lol. Not sure though.

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yeah the reason running rich is better than lean is because the only thing you'll be doing is running more fuel through than can burn off, so you're more apt to foul plugs and ruin your cat, but that's a lot better than messing up internals.

Also, running rich results in less optimum burn, which means less power output, and of course, much less efficiency (your primary objective).

yeah, agreed. It's pretty crazy how the 3800 gets the fuel economy it gets. Especially in a car that weighs 1.5 tons. I guess it just has to do with the torque curve and the gearing. The engine has such a broad torque curve that the gears can be longer without working the engine so hard. In turn you get much lower gearing and higher fuel economy.