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Mopar 2.2 and 2.5 TBI Power Upgrades


What is a TBI engine?

Mopar Muscle magazine

The TBI engine is essentially any 2.2 or 2.5 with fuel injection but without a turbocharger (some exceptions were been made in Mexico). These engines were used on many cars, minivans, and light trucks. The computers and the engines underwent many changes as the years went on.

While turbocharged engines had multiple-port fuel injection (each cylinder had its own injector), the TBI models had only one, which is considerably less efficient - and that is one reason why the Neon 2.0 has 132 horsepower and 129 lb-ft of torque, while the 2.5 TBI engine had only 100 horsepower (albeit with 135 lb-ft of torque). David Zepeda tells us that the 2.5 liter engine in Mexico, where multiple-port injection was sometimes used instead of TBI, reached 110 hp, but gas mileage cannot be compared, and other adjustments may have been made to adapt it to high altitudes and lesser gas. We've heard since then that some turbo TBI engines were sold in Mexico in the 1980s.

Modfications to Chrysler/Dodge/Plymouth 2.2 and 2.5 liter TBI engines

There isn't much you can do (cheaply) to a TBI engine, and the following modifications may not affect your performance too much. The most common advice, "get a turbo!", is not always practical, though we have a comprehensive TBI-to-turbo conversion page.

The 2.2/2.5 TBI engines were competitive at the time they were made, for most of the models they were in (e.g. Sundance, Omni, Reliant). In the lighter cars (Omni, Reliant, Charger, etc.) with a five-speed, they could be quite quick; however, as Dan Stern points out, the automatic transmission's gearing did not help much. Again, even with an automatic, they were usually competitive in their price class, e.g. against the Cavalier, Escort, Tercel, and non-EX Civics (the EX added 25 horsepower and quite a bit of cash, taking the Civic out of EEK territory unless you were talking turbo-EEK). The 2.2 liter Reliant or Omni, with a five-speed, can keep up with most current economy cars.

These engines have nice low-end torque for four-cylinder models but are lacking in horsepower due mainly to poor breathing and fuel starvation. With good heads, MPI, and turbocharging to get air in there, the 2.2 was capable of high performance. (The 2.5, due to its long stroke, tended to be less racy in the high revs, but was quite satisfactory for most street use).

Dan Stern: Mexican parts

There are lots of interesting components and systems found on Mexican-spec 2.2 and 2.5 engines that we never saw here.  For example, all of the non-turbo AA-bodies got multi-port (rather than throttle body) injection, but some of the 2.5s lacked balance shafts.  Many of the engines had a very nice factory header system, and of course there's always the 8v 2.5 intercooled turbocharged engine used in the "regular" Spirit R/T and Phantom.

Edward Kelly:

I am not sure if there are any performance cams for the normally aspirated 2.2.

If you have some $$$ to spend you could have the head ported, 3-angle valve job, back cutting of the valves done, port matching of the manifolds. Back cutting the valves and 3-angle valve job will both help the head flow better especially at low valve lift... The valve guides are probably worn, you can have them replaced or spiraled to bring them back into valve guides will last longer. Spiralling is cheaper.

The porting is probably the most costly and also the most difficult to judge effectivness... That said, there are some simple things that can be done that will be improve the flow. This is especially true [if] you aren't looking for max performance, just improved performance.

Shaving the head to up the compression ratio would also increase hp. If you shave it too much you will need to run an oversized timing belt tensioner or an undersized belt (both sold by MP). You may also need to run higher octane fuel. If you decide you don't like the increase compression, you can get a copper shim gasket (Felpro makes one) to move the compression back to stock...

Degreeing the cam will also help...

Ted Raisor noted:

There is a long tube super competition header for 2.2 and2.5 equipped cars available from Hooker Headers. It only lists up to an 1988 but I know it also fits an 1989 daytona. Also I have a set of Eibach 1" drop springs on my Daytona but you have to buy them for a Dodge Spirit. And I've squeezed a little more top end power out of my TBI by cutting a hole in the hood slapping on a scoop, and using a Spectre intake tube to connect to the air box; all I had to do was make a tray and bracket and put some foam on it

Derek Beland wrote:

The problem with tweaking TBIs is that very few changes are individually noticeable. Most mods you can make will yield an increase in power that is a factor of the baseline power from the factory. Baseline power being rather low at 95-100hp, gains come in 2-5hp increases.

Some ideas are:
- advance ignition timing to 15 degrees
- play with cam timing via offset keys
- K&N drop in filter
- remove intake elbow
- remove heated air flap in airbox inlet
- hotter coil, wider plug gap
- cooler thermostat, remove coolant lines to TB
- bore out TB
- modify butterfly (shave shaft, shorten screws, knife edge leading side)

The expensive/time consuming stuff:
- ported head
- bigger valves
- convert to carbs
- shave head to raise compression

This assumes of course that your engine is in top running shape. A compression test might be wise, and potentially a ring-job. Beware that performing enough of these mods will run you lean. Get an air fuel meter to tune with, like any other motor!

There are differences between the later model TBIs and early ones. My stock fuel pressure is 39 psi for example, so I'm sure the injector is a different flow rate as well. My head has the "TS" stamp on it, which Gary's website says indicates a turbo head - but this one is definately the original. Perhaps flow is better. I know the intake manifolds for later models are slightly different. There was a TSB about hard starting that indicated the manifold could be switched to a later revision to cure the problem.

I don't want to upset anyone, but the automatic tranny TBIs are dogs. The previous owner of my 5-speed 92 car was given a loaner while they worked on it, and the loaner was identical in every way - except it was auto. "Couldn't get out of its own way" were his words.

Most people have to mod what they have. It doesn't stop the Honda guys though! They'll slap cold air intakes and headers on their cars to the point that if they summed up the total expense, I'm sure for a bit more they could have bought a turbo kit. I don't propose being that dumb, but I don't think it's unreasonable to think you can get another 20-30hp out of the motor, with a reasonable budget. My goal was only to be able to keep up with (hopefully a bit more than!) the 16V Cavalier & Sunfire class of cars on the road, not to make a track-dominating monster. :)


I like my MSD6A [ignition system]. Cars pulls to redline at a steady speed, vs running out of steam at the higher RPMs. Lots of other people say they do nothing (particularly the turbo crowd). I have my car setup so that I can bypass the MSD and run straight to the coil, and there is a small but noticable difference. Is it worth the $200 price tag? Dunno, that's a subjective thing I guess. BTW, you need to mate it with a Blaster 2 coil.


Timothy Pindell wrote:

I took my Daytona to the Nats for a few passes. My reaction times were abysmal, but the car is now capable of mid 17s with a good reation time. Here's what I did to mine for "race" day:

  1. MP camshaft P4529320 252/252 duration, 36 overlap, 108 centerline, (uses factory .430 lift)
  3. Accell super coil, .05 gap on the Champions
  4. ignition timing set to 15 advance
  5. fuel pressure raised to 15.5 psi (it idles like crap, not sure if it's cam or fuel pressure related but it is lopey and sounds cool)
  6. removed rear seat, spare, jack
  7. 2 gallons fuel
  8. removed AC and PS belts
  9. rear tires to 55 psi, fronts to 35
  10. removed air filter, left the box
  11. Dynomax muffler/ 2.25 exhaust from the manifold/ no cat (it's rather loud with a straight-pipe edge to it)

I shifted at 6200! (indicated) rpm. Yep, it was still pulling, but not much.

This illustrates my belief that you can't get much out of a TBI unless you go lots more radical. It's got a bit more than what it had when it left the factory, but not as much as the tubo guys get for the same effort. Don't teach a TBI to go real fast. It wastes your time, and annoys the engine. (But it's fun to experiment =] )

Summary of low-buck approach

David Reynolds wrote: "the best performance you can get from a 2.2L n/a car is to be had by (in order of expense):

  • advancing ignition timing to 14-15 degrees (free)
  • K&N drop-in filter ($35)
  • 2.25" exhaust (around $100)
  • raise compression *a little* by shaving the head and/or block ($$$)




2.2 / 2.5 TBI breathing



Herb DaSilva wrote: "Smooth out the exhaust - there are several ultra-high flow cats on the market - go 2-1/4 all the way back to a turbo-flow muffler."

Bradley Miller suggested: "Daytona/Laser mufflers will fit our cars. (HINT!) Stock pipe is 1 7/8". Lambros Race Engineering has an adjustable fuel pressure regulator that will allow for fixing lean conditions. They also have different gear ratios (provided you don't mind losing top end) and they have different pulleys. This will spin the accessories a little slower to reduce parasitic horsepower losses." He later wrote: I just got my exhaust on Friday. It really helped with the sound of the car and the mid-range pull. I've now got 2 1/4" pipe all the way back to a Walker Super Turbo muffler. You can step down on the accelerator and really get a good shove in the pants without the car downshifting. In the upper RPM bands it doesn't really help too much. suggested using an exhaust wrap, to keep heat in the pipes and maintain exhaust gas velocity. He also suggested using a TBI spacer of at least an inch to help out the low end.

Derek Beland wrote:


The installer talked me out of putting a bigger pipe on -- I'm glad he did. I wouldn't want to lose any more torque than I did (cause then it'd be a Honda).

Click here for muffler replacement instructions, tips, and stories

Jerry Adams warned:


So I went looking for a substitute that would flow freely and be very efficient at stopping the abrasive particles. I found several oiled foam air filters - HKS Super Mega Flow, Amsoil, Finer Filter, Dura-Blue and Accel. I reviewed the available test data which showed K&N flows more air and more dirt than paper - as I suspected. It also showed the oil foam flows more air than paper and almost equal to K&N - except K&N's data showed their filter best. One test [for motorcycles] suggested using K&N only for road racers and use oiled foam for dusty conditions.


[Webmaster note: the test results Jerry referred to were made on motorcycle magazines, which may or may not affect their applicability. There is a lot of controversy over the K&N filters.]

Bradley Miller wrote:

    Before you get your injectors (uh . . injector for TBI), check to see what you are actually getting first. Everyone is concerned about airflow and going lean on the 3.0L engines and I have yet to see anything near too lean with my modifications. I suspect you'll find the same with the soda straw limitations of the TBI intake...

    Rule number one is, don't add more fuel till you need it. Ask any of the turbo guys and you'll realize that bigger injectors is the first purchase that bites you on the butt with a stock computer and boost level. Tricking your computer for more fuel flow without any work to the head or the TBI itself would be in that category. Typically most hotrod computers for other brand-x cars actually lean the mixture out. The same would hold true here I imagine -- but find out for yourself and document the changes. I did all the bolt-ons I could within reason on my Duster and didn't see any neglible improvements. Going from 100 to 110 hp in a 2900 lb. car . . . well you get the picture.

Intake manifold



Air filters and related stuff

Dave wrote:

Keep the filter clean: on my Sundance, all air goes into a 2 inch square section of filter, which gets filthy quickly, while the rest of the filter stays clean! IMHO, the K&N, by itself, does little to improve performance. It is cleanable and pays for itself in replacement air filters if, like me, you are conscientious about replacing those things.

Bradley Miller said:



Using cone filters on cars that K&N doesn't make cone filters for

Webmaster note: Though this is a common performance practice, bypassing the standard airbox may result in longer warm-up times, especially during cold weather, because when the engine is not yet at operating temperature it "recycles" heat by taking air from around the engine itself, rather than from the outside. This really does make a dramatic difference in warm-up times (you can find out for yourself by disabling the switch!). In addition, EEKs cool the computer using the air going into the engine; some have hooked up small 12V fans to blow at the computer instead (standard computer fans work). This is really a modification for those with high-performance engines (e.g. Turbo III/IV) or those who have already done other modifications to increase power and airflow.

Paul Smith:

The hose from the back valve cover to the Air Box pulls air into the engine, where it is sucked in by the pcv valve. It would be wise to filter this intake air along with the main air intake.

On the K&N filter. I went to Auto Zone, looked in the catalog, found a filter size I liked and ordered it. Mine clamps onto the throttle body with a hose clamp. The one I ordered was actually for my turbo inlet, but same principle. K & N makes all sizes of "cone" filter to clamp onto a pipe or nipple or throttle body. You can get them 2" long, 2" dia, to clamp onto a 3/4" pipe, all the way up to 6" dia. 8" long and bigger. The have filters to clamp onto 2" pipe, 2.25" pipe, 2.375" pipe, 2.5 pipe etc. etc., with lots of sizes for each pipe size. I picked the RU 0640. It fits on a 2.25 inch pipe, and is 4.5" dia, 5.5" long. $36.00 You could also get 5.5" dia, 7" long, $39.00, or the 4.5" dia, by 4.5" long for $32.00. What I am saying (in a real rambling drug out way) Is that they could get like 20 different size cone filters just for the 2.25" pipe, with lots of choices for EVERY size pipe you could want. Just measure the dia. of what you want to clamp it to, and buy the biggest one that will fit. They order it, and you have in two or three days.

Mark Housley wrote:

I just cut the intake hose close to the end (around the ribs where the filter clamps on) and made my own little adapter to use with the 5.0L cone filter. Paul Berkebile did the same. It was his idea.

Another take on this process

Andrew Dodd wrote about Matt Karl's ram air mod, posted on Matt's web site.

You'll need the following from Home Depot or a similar store - Prices in $US

  • 3" aluminum heater ducting - $5.49 or $5.99 for an 8-foot length. (8 feet is its maximum length - it starts out much shorter, and you can expand it as needed.)
  • 3" pipe coupler
  • 2 3" worm clamps (aka hose clamps)
  • 1 4" worm clamp

Remove the stock air hose from your airbox/intake - pretty easy, it's not on there very tight.

Snake the heating duct downwards through the space between the radiator hose/electrical wire and the transmission housing. It's a tight fit - Getting at your tranny dipstick will be a bitch after this mod. Once you have a bit, stretch it out and route it to the fascia, right between the two holes. If you don't have enough, stick more down. :)

Stick the 3" coupler into the end of the ducting. You'll want it relatively far in (but not all the way.

Open the 4" clamp all the way, and thread it through the holes. Use it to fasten the coupler/duct assembly there. MAKE SURE that the clamp is ON the ducting, if it's just on the coupler, it WILL fall out. (Trust me, been there, done that. :) Tighten it down, keep on feeling the assembly for sturdiness. It'll be a bit squashed and oblong by the time you're done.

Use one of the 3" clamps, install it around the ducting/coupler just behind the 4" clamp. (Just around the coupler/duct for this one...) - It's probably unnecessary, but I have it on anyway just in case.

Stretch the uppper portion of the pipe to the airbox, and clamp it to the airbox using the last 3" clamp. You'll have to tighten it down a lot - the airbox only has a 2.5" inlet.

You might want to use RTV to seal everything, too. I haven't yet, I will do that when I mod my airbox.

This mod doesn't reach its full capabilities without a K&N filter. I haven't noticed too much difference except at highway speeds. (Around 70 MPH is where I start noticing a big difference - This number will probably decrease a lot once I put in a K&N and mod the airbox, I believe what's happening is that at around 70, the airbox just isn't able to leak any more of the excess air, so it FINALLY starts getting forced into the engine. :)

Andrew clarified:

Jury is out as to whether this helps on the Spirit ES with the air dam on the front bumper - It may be preventing air from getting to the intake. I still can't tell for sure whether I've had improvements, other than the highway, and even then highway driving at those speeds is so rare when I'm at school that I can't be sure. People without the airdam/foglight assembly (less blockage) have had good success. (Shadows, non-ES Spirits).

Also, 4" to 3" reducers to replace the coupler are bad news. They reduce ground clearance just enough to get ripped off easily. Basically, using a 4" to 3" reducer (with the large side facing towards the front) adds a half inch radius to the whole thing AND results in the forward lip of the reducer being about an inch or so farther forward than when using a straight coupler with the front lip even with the front part of the fascia. It's JUST enough to make it very easy to rip the reducer off going over large bumps. (Whereas with Matt's intake as described, you just have to be careful about curbs when parking).

Matt seems to have found a stiffer coupler than what most of the other EEKers have been using. The ones we've used are thin aluminum and distort easily.

Martin Rempel wrote:







Sensors and stuff

Some advise a lower-temperature thermostat (e.g. 180 degree) - this is fine if you want to pollute more and lower your gas mileage, but is not really a sensible way to run your car. The engine was designed to have a certain amount of heat, and preventing it from warming up fully in order to keep the mixture rich is not the sort of thing we'd expect from Mopar folk.

Bradley Miller wrote: I was concerned that I might be running into a lean condition, the car gets a bad "soft spot" in 2nd and 3rd gear with a load. I haven't tried this yet, but they suggested a "poor man's lean/rich" sensor. There is generally three or four wires from the O2 sensor on the exhaust manifold/pipe. One of these will be either 5 or 12 volts positive. One or two will be ground and one will be the sensor lead. Take a voltmeter (DVM, not an old analog) and probe to find the correct wire. They said to connect the DVM and monitor the thing at idle with the + lead of the DVM hooked to the sensor wire and the - to ground. You want the setting to be in hundredths of a volt (if your DVM isn't autoranging). The thing should bounce around on voltage readings at idle. (Make sure you've warmed up the car for a little while.) By hooking the thing up inside the car, (tap into the wires and run into passenger compartment) you can monitor the conditions of the fuel/air mixture. Lambros stated the voltage should be form .88 to .94 volts during acceleration (load). Any lower than this is going to be lean, and any greater is going to be rich. Now, I don't know for sure if these numbers apply to all cars. Their number is 314-725-7181. They will be more than happy to help you. These voltage numbers should apply to TBI normally aspirated cars. This test will also show if your O2 sensor is working properly.

Fuel injection






The complete side draft Weber kit from Pierce is: $823.20

The side draft Weber manifolds, it's $293.24

They can be reached at:

Pierce Manifolds
321 Kishmura Dr.
Gilroy, CA 95020

Camshafts and balance shafts




[Dan Stern wrote, "there isn't much to be gained and quite a bit to be lost in the way of livable engine operation" - a statement which Gus essentially agreed with.]


Bradley W. Miller wrote:






John Basol wrote:



  2. High Energy
    Powerband: 1200-5000 RPM 22-123-4
    Powerband: 1500-5200 RPM 22-127-4
    Powerband: 1800-5500 RPM 22-131-4
    Powerband: 3000-6000 RPM 22-124-4










Match porting

Vincent Cheng wrote:





TBI to Turbo

Maurice Barrett wrote:



(On using Weber side-draft induction)


(On a $3,000 cost estimate)



Timothy Prindell wrote back:



Some suspension notes










Stefan Mullikin's 2.2 - 2.5 equipped car upgrades








Dynomax Street Systems

The setup is available for these Mopars (cost is about $100 plus shipping, except for the Neon, which is about $150). Make sure they throw in a reducer (part 35253) for your convenience (not available or needed on Neons).

The street system, according to people who have installed it, gives a nicer tone - not too loud, but deeper and more mellow. It looks like stock unit, and comes with mounts, clamps, and a tailpipe. It is not a catback system.

  • Part 17488:
    • 84-86 Laser 2.2 & 2.5
    • 84-91 Daytona 2.2 & 2.5, including Shelby, ES, IROC
    • 86-89 Lancer/LeBaron GTS 2.2 & 2.5, including Pacifica]
    • 87-94 Shadow/Sundance 2.2 & 2.5
  • 95-98 Neon 2.0

Part 17488 includes the over-axle pipe, muffler, and tailpipe; the extension pipe, which on turbo cars (and some V6 models) is part of the catalytic converter, remains stock.

According to Benjamin Hook, since Dynomax only offers the rear section of the exhaust, a Dynasty and an Acclaim would interchange, if a system was available. However, Dynomax part 43262 (over-axle pipe) will fit any EEK, except minivans. "It orients the muffler straight out the rear of the car, instead of towards the left rear corner like on AA and K bodies, giving a better performance look." Bejamin said he has used this pipe with good results on Spirits, Daytonas, Omnis, Sundances and Reliants.

Mike Holler’s mods and repair tips

Red carpet treatment: Installing new carpet in an old car
Headliner repair
Porting Porting heads for performance: step by step
Head porting example, part 1 | part 2
Intake manifold porting
Exhaust manifold porting (turbo)
Poly Quad heads: porting revisited

Turbochargers Turbochargers - all you need to know (interview)
Budget turbocharger rebuilding (and Turbo Rebirth)
Installing a boost gauge

Other Powder-coating for a brilliant, durable finish
Custom pistons: roll your own!
Prepping valves for performance: grinding and polishing
Old cars: an opinion
