Ive got an 88 IROC with the 5.7 TPI that I use as my daily driver...I was thinking of just up grading the TPI but after putting some minor up-grades (ZZ4 heads, underdrive pulley's, Hedman longtubes to true dual's) Im just plain tired of the shitty MPG and low power: Estimate 250hp and averaging 12MPG

So I've been thinking of a motor swap hence the thread. Im not sure what motor would be best for me I want to reach 300-350 RWHP while maintaining decent MPG and while still doing so within a budget. So what would be the best choice for me? LT1, LS1, 5.3LS, 6.0? Im just not sure so what do you guy's think?

 

Try getting rid of the TPI and putting a decent intake on it instead.

Either the Stealth Ram or the MiniRam.

 

I thought about that but Im still stuck with the shitty MPG this is my DAILY DRIVER so I cannot afford to get 10-12 MPG...

And I would like to get a different DD but I cant do that right now because Im about to launch a small business.


One thing I forgot if you have the swap's I listed above if you could list average cost I would really appreciate that.

 

There's not really any such thing as "average cost"; those are all JUNK engines, meaning they come from WRECKED cars as opposed to just being soemthing you can just up and order ("yes mr junkyard will you please have somebody go out and wreck a 01-02 Z28 or Trans Am today for me") whose price depends on how many miles they have, how plentiful they are, and how much the JUNKYARD thinks they can get for them. Price is all over the map. Could be anywhere from $3000 or so, on up to easily $10,000 or more. Depends on what level of detail you want to perfect it to, how much of the new motor you get, how much of the work you do yourself, etc.

I can GUARANTEE though, you can do about 4 or 5 intake swaps for what 1 LS1 swap will cost; and about ¼ the trouble.

Meanwhile, there's no reason you shouldn't be using less gas than that. Sounds like it's time for some tuning.

When you burned your latest PROM, what kind of constants did you put in it? What kind of condition are your injectors in? What does a wideband O2 read on the chassis dyno, both under WOT conditions, and typical cruising?

 

I have not burned a PROM why would I have to?

 

Because you've changed the engine's fuel and spark requirements.

In older setups, you do that by tunign on the carb and the springs & weights in the distributor. In an EFI system you do it with the programming.

No there are no hand-held programmers that work on these ancient computers. If you think about what you were surfing the web with in 1986 (the year that computer was introduced) and compare it to what you have now, or compare your cell phone from back then to a current one, you can apply the same comparison to your car's ECM.

No there are no off-the-shelf "chips" you can buy that will have the correct curves for YOUR combo. To get it perfect, you have to do that work yourself.

 

would something like this help?

http://www.pcmforless.com/index.php?...per&Itemid=312

 

Mail order tunes work if they have dyno tuned a combo exactly like yours. If there are any differences, even subtle ones, the results can be disappointing.

FWIW, my two LS1 swaps were out at the track recently. The LS1/4L60E car made 14 passes between Friday evening/Saturday, when filled up on Monday with 308 total miles (commuting and those 14 passes), it averaged 16.9 MPG. Similarly, the LS1/T56 car made 4 passes on Saturday, 285 total miles (commuting and the 4 passes), averaged 20.1 MPG.

The LS1/4L60E runs low-13's at our 5800' elevation (12.2's at sea level), and the LS1/T56 runs mid-13's (12.6's at sea level). The only tuning I've had done was to eliminate things like VATS, skip-shift, torque management, uninstalled emissions equipment, and set the gear ratios and tire sizes I'm running. Things like fuel and spark tables haven't been touched.

 

That includes the one you linked to. No better than any other. All WRONG unless your engine is PERFECTLY bone-stock, and whatever your goals are happen to align exactly with whatever theirs were. For example, would you trade a little cold-weather driveability for a few more HP, a little throttle crispness for fuel mileage, a little snappier response for being able to use regular gas, etc. etc. etc. etc. It's all a big balancing act. Give up one thing, that YOU think is less important TO YOU, to get something else that YOU think is MORE important TO YOU. Nobody else can make those choices for you.

Five7 touched on one of the advantages of the newer engines; they are considerably more efficient, in general. So there's a potential cost advantage there if you drive it alot.

 

How about 400+ rwhp with better street manners than a stock TPI. 26mpg on the freeway/16mpg on the street sound?

LSx is the way to go. 5.3 and 6.0's are selling for cheap and make great candidates for economic swaps. Bare bone 6.0 builds for under $4k if you do the work yourself. They'll easily get you to your hp goal without h/c/i etc. There are tons of LSx tuners out there vs. small dying breed of proms burners.

Check out the LTx/LSx forums.

 

if your getting that low of milage you have a problem that's not just because you have a TPI set up. I have a 5.7L, zz4 heads, zz4 cam, 3.73 rear gears, headman long tubes, and a stealth ram, I'm knocking down 20+ easy on the highway. granted I have a t56 but thats not worth 8 mpg maybe 2 max.

 

Exactly: TPI may be the clear-cut cause of low power output, but is capable of somewhat decent gas mileage.

OTOH, it is more sensitive to component mismatches than many other intake systems. More easily upset, as it were.

 

Well if I'm only hwy ill get around 18mpg with no ac and a 700R4 as of right now I'm looking into a 5.3

 

You've got a problem not caused by the TPI. Even the EPA rated your motor for higher mileage than that at 15mpg city http://www.fueleconomy.gov/feg/findacar.htm. You need to do a leak down test. Something is wrong with that motor. Maybe the rings are gone and you need a rebuild. Or maybe you need to change the plugs or module. But something other than the TPI is causing your crappy MPG

 

hopefully hes figured something out in the 2 months since this thread started....to the OP, if you ditched the TPI, ill take it off youre hands . I need it for my 86 silverado.

 

I have to laugh alittle to myself when I read post like this. I got a bone stock L98 mated to a T56 that has all bolt on upgrades which includes new injectors and tune, and I get better gas mileage then my 4 banger Mitsubishi Galant. You need to tune that thing....