The 2.5 uses more gas due to the longer dwell time at the top of the stroke and the larger bore. You'll notice that more car manufacturers are going to with smaller and smaller motors to increase mileage.
If you're electrically competent and patient you can use a turbo intake with MegaSquirt to get proper fuel injection as the TBI solution is woefully inefficient and the wiring work is similar to either solution. The biggest improvements I've seen in a non-turbo Omni is simply getting the induction working properly. This means messing with the poorly made carb quite a bit or simply ensuring the fuel injection sensors and wiring is in good shape. The suspension is relatively easy to upgrade. Look for off the shelf GLH-style parts to use: Faster ratio power steering (2.5 turns lock to lock can be bought rebuilt from the parts store) Lowering springs (either stock GLH or via the aftermarket) Stiffer shocks/struts (Koni or custom is all that is really left, KYB's are simply OEM replacement) Swaybars are available and using an endlink style sway bar will help the suspension move and not bind. Reducing suspension bind will improve the consistency of the handling and the ride comfort. Strut tower braces are nice, but unless you're really pushing the car, it isn't really needed. Larger brakes are available from similar year Daytona's/Lebarons, etc don't go with 4-wheel disc unless you're really into it as it can mess up the brake balance. A set of properly adjusted 220mm rear drums are more than enough, IMHO. Note: You can stay with the 4-lug hubs and get the larger vented discs, just use 84 GLH rotors with the calipers and brackets from an early minivan or K-car. and the 84 topline cars had 220mm rear drums. However if you are planning on upgrading the wheels/tires I would suggest moving to 5-lug hubs since they are stronger and finding wheels aren't much harder. If the car is a 5-speed you can improve the transmission by using an A-520 or later transmission (do some research on the drive ratios as the 555's, etc can have some uncomfortably tall 1st gears and that will affect how peppy the car feels) Shiftlinkage is a sore spot. Upgrade to metal joints in the stock linkage or go with a cable shifter. If the car is an automatic, there are some basic tricks available to improve the shifting by changing a few things in the valve body. A full-manual reverse valve body is also available. Either way though, the automatic sucks the meager amount of power available from the car and decreases the mileage. I'm not a big fan of them and I feel that if you want to drive, you need to learn to drive a stick. It helps people understand that they need to pay attention to the car, not to their phones, lattes, passengers, etc. Plus I find it much more satisfying to row my own gears. I've made a number of other minor improvements on our GLH-Turbo just by shopping the Chrysler parts bin. Replaced the power steering pump with a later model ZF unit that is lighter, uses better fittings and is easier to adjust. Use the lines from the donor car, make note of the year/model for replacement part sourcing. Replaced the Big, ugly Bosch alternator with a newer 120amp Nippendenso unit. Again it is easier to deal with because it is smaller and in the tight engine bay of an Omni, that is an important selling point. Make sure you upgrade/replace the wires for the battery/charging system while you're at it. A smaller, lighter battery will help reduce the weight on the nose. Some go so far as to move the battery to the trunk, but that can be turn out to be a negative since you have to factor in the weight of the longer cables and the battery box. On my Rampage, I ran a Mopar header and it helped improve the mid-high range power. The trade off was that it was much noisier and more prone to cracking (better motor mounts and rewelding the flanges helped) If you have to change the headgasket, getting the head shaved can up the compression ratio (the High Output Shelby motors ran 9.5:1 compression ratio) you'll need to use an adjustable cam gear or cam gear keys to correct the cam timing afterwards. Along with higher test gasoline. Head work can make a difference to a certain extent, but you'd need to pay attention to the entire intake/exhaust system and not go too far since the stock intakes don't flow all that well. If I were to build a non-turbo SOHC motor today for the street/fun, I'd use a 2.5L block with 10:1 compression ratio pistons. Put a bunch of money into the head to increase the quality of flow (not just the quantity). Use a header, modified to be 4 into 2 into 1 with a 2.25" exhaust. Depending on the budget, I would either run a sidedraft Weber intake with Weber throttle bodies or I'd run a stock 2-piece turbo intake. Either intake solution would be controlled via MegaSquirt with distributorless ignition. If the sky were the limit, I'd ditch the stock SOHC head and convert the block to run a Neon/Stratus DOHC head. Or mount a 2.4L DOHC drivetrain in the Omni. Cosmetically, the GLH air dam and side skirts help make the car a little more sporty, but they can be be hard to find. Blacking out the gril, headlight surrounds and mirrors can toughen the little car up a bit. Shelby Charger seat covers front and rear is a nice look, I've seen but have never been able to accomplish yet. Adapting other mirrors might work as well, but I've never tried it and you'd need to clean up the adjustment holes on the doors somehow or make use of them. On my Rampage, I used Daytona leather seats up front. they sat a little taller, (not as much of an issue with an Omni and the Charger/Rampage seat rails were slightly lower) but they were much more comfy. I just adapted them to the Omni seat mounts with some steel flat stock. I've seen pictures of someone using a 91 Jetta big-bumper cover on the front to modernize the Omni a little. Mercury Sable sideskirts should fit with a little work or you can wander the yard some looking for something that might fit better. The person who did the Jetta bumper cover said that the Jetta rear cover will fit with some work as well. That's about all I can think of for now. If you hit up Google and do some searching for some of this stuff you might find more detailed posts about it on Turbo-Dodge/Turbo-Mopar and other sites. FWDMotion, TurbosUnleashed and FWDPerformance all have experience with the cars and can provide some advice and some hard to find parts as well as performance parts for the car. Good luck, Stefan Mullikin Portland, OR PNW-SDAC Founding Member 1979 Porsche 924 (Carrera GTS Replica and GRM $2007 Challenger) 1980 Fiat X-1/9 (never ending 2.2 turbo swap) 1984 Dodge Rampage 2.2 1987 Plymouth Sundance Turbo (Daily Driver) 1987 Shelby CSX #106 -------------- Original message ---------------------- From: [EMAIL PROTECTED] > Changing to TBI would be more reliable, but I think the milage would suffer a > bit. I don't know for sure, but I had fantastic mileage with a carbed 2.2 > (and > turbo's) and can't seem to get close to that with a 2.5 tbi. This also may > be > the year of cars. > > > > Bob Doherty http://amoparx.net/mnsdacpic/mnsdac.htm > Coon Rapids, MN. > > 89 LeBaron GTC Convert TII > 87 Shelby GLHS #784 > 87 Shelby GLHS #654 http://amoparx.net/glhs654/glhs654.htm > 68 AMC AMX #5816 http://northstaramc.com/northstaramc.html > 94 Plymouth Sundance 2.5 TBI (My Wifes car that I drive) > http://geocities.com/amoparx/ > > > -------------- Original message -------------- > From: Rich Bryant <[EMAIL PROTECTED]> > > > > > IMO The best mod for the car is to pull all of the carb stuff off and swap > > it to TBI fuel injection. I did this on my 87 Turismo and it was a much > > much more reliable car. It no longer stalled when cold and it ran much > > more smoothly. It wasn't however a big power boost. It was a lot of > > work though... > > > > Without swapping the actual engine out that is about the best option in > > addition to the other mods suggested. Overall The car is going to be > > stuck at 100hp without a cam, or turbo or some headwork. > > > > The turbo is a good option but I am a pretty firm believer that kids > > should have slow cars to drive. :) > > > > -Rich ___________REMOVE-FOOTER-WHEN-REPLYING_________ ShelbyDodge mailing list [email protected] http://www.imagilist.com/mailman/listinfo/shelbydodge
