MODS You Don’t Need

Apr 8, 2008

With so much talk about what to buy, we figured an appropriate topic would be about which mods not to buy. Not buying the wrong things can be just as important as buying the right things. There are plenty of people with a lot of money, and there are plenty of companies selling mods, yet there are only a handful of people running record times. Much of this is due to those people knowing what to buy, and what not to buy.

Here in Grand Rapids, MI, we modify a lot of Grand Prixs. We also get a lot of customers emailing us about what times they want to run and what mods they currently have. Making it very easy for us to see what works, and what doesn’t. Doing installs also allows us to see how close to optimizing their existing mods people actually are. Simple mods like pulleys and air boxes can be very straight forward, but as you get a little more advanced, and increase the number of things you have changed on your car, it then becomes a lot more difficult to optimize your combination. It is for this reason, and a few others, that your goals should be achieved with as few modifications as possible. 

Most of our customers spending $5,000 or more have already purchased a lot of products and are usually disappointed in the way their car performs. The first thing we tell them is that they have to ‘de-mod’ their car. These guys will leave with a box of their old parts to sell, a fast car, and a setup that is much easier to tune. Tuning is essential; without properly tuning your vehicle, you’ll be stuck in the mid to high 13’s for the remainder of your Grand Prix racing career.  Modifying parts by term is to change what the factory did. We all have things that we would like to change about our car from stock, but one thing I can tell you is that modifying makes your car less reliable. I don’t care what the modification is, if it makes more HP, it will make your car a little more prone to breakage.

An exception to this might be removing parts that you don’t use but we’ll talk about weight reduction later.  Since no one wants to make their car less reliable, it stands to reason that things should only be changed when there is a need to change them. Tricking your ride out can be costly, and money wasted on an unnecessary mod could be better suited on something else.

Transmission coolers

The idea of a tranny cooler is a good one. In theory, if you keep the transmission running cooler, fluids should stay cleaner and parts should last longer. The problem is that Grand Prix don’t have a problem with transmission temperatures. A tranny cooler might be a great idea on some cars, but the Grand Prix is not one of them. Little known to most, is that the GP PCM monitors transmission temps, and if the tranny temps get too high, the PCM will set a check engine light and possibly take precautions to limit abuse.

Here is a quote from INTENSE racing (they build performance transmissions for GPs) “Should I run a tranny cooler?”

“Only if you’re planning to pull a trailer through the mountains. Otherwise, we recommend against it on vehicles with the 3800 FWD/4T65E drivetrain.”

We have dissected more of these trannies than anyone else in the performance after-market, and we have yet to see a single heat-related failure. Hard parts break in these trannies, and these failures won’t be prevented by a tranny cooler.”

We have also done dozens of transmissions here at ZZP, and we know from opening them up, that a tranny cooler is not helping anything. We’ve seen tranny’s break with 50 miles on them and others with 125k on them. Problems have NEVER been related to fluid temperatures or fluid break down.

We are at the point where we can’t convince our customers to take off their tranny coolers, or to not buy one, we often hear the response “well, it can’t hurt” or “I’ll just play it safe”. Transmission coolers have many down sides. If you recall at the beginning of the article, we broke down all the reasons not to buy unneeded mods, and the tranny cooler is no exception and here’s why:

We have rebuilt more than one tranny due to a failure of a tranny cooler. When your cooler leaks it can cause very serious problems. Below is a pic from a car in Grand Rapids where a severed line left this owner in the cold. [No photo attached]

Here is a quote from a member of the RegalGS forum:

I installed the GM cooler 10 plus thousand miles ago along with the Thrasher shift kit. (second setting) I’m a bit “old school” when it comes to these things. I figured if the cooler is on the Police Impalas, it would work with the GS trans nicely. Further, I do have a hitch on the car and haul a small trailer on occasion. For me, I feel more comfortable in using a cooler.

However, during the installation, I double clamped the lines and triple-checked for leaks. There were no leaks and the installation worked great for a while…until…on a WOT jaunt up a back road on my way to an appointment, I noticed a bunch of smoke behind the car. I stopped and looked under the car and noticed fluid pouring out of the front of the car. I thought it was antifreeze and traveled another two blocks to the appointment where I finally opened the hood. FIRE! I carry a fire extinguisher in the trunk and the fire was put out quickly. There was no damage from it either, thank god!

It turns out, one of the “double clamped” lines blew off the steel line and sprayed trans fluid all over the exhaust manifold. Fortunately, I was two blocks from the dealer. Still, I had it towed, I didn’t want to risk more fire and a bad trans. The dealer replaced the lines and flared the ends so the re-clamped rubber lines wouldn’t come off again. Just a little story of my experience.

With nothing to gain and a lot to lose, you can see why we are so strongly opposed to tranny coolers. Even if the cooler doesn’t fail, you are adding weight to the car, costing yourself money and blocking some of the airflow to the main radiator which in turn makes the car run hotter costing you HP. If you have a car in a very hot climate or car with a turbo kit, we suggest our oversized radiator to properly take care of the heat issue.


Aftermarket Plug wires

Unless you have a problem with your stock wires, you don’t need to buy aftermarket ones. In our experience of working on GPs, the failure rate of most aftermarket wires is 10 times that of stock wires. GM puts everything they have into making cars get the best mileage they can with the least amount of problems. A poor ignition system would increase emissions, which GM couldn’t afford. This means plug wires from the factory are designed for high spark, low radio noise and excellent performance. If you’re set on upgrading them forget about MSD and Jacobs.

The regulator controls the power of the factory ignition module in the 3800. The MSD wires have almost no resistance which puts a large demand on the coils to produce a lot of current (Ohm’s Law). Since the ignition control module limits the current to the coils, you end up with a poorly performing system. This is probably why we gained a consistant 4 HP going from MSD to our new ZZP wires and why MSDs have performed poorly in our high HP builds.

Air temp modules

An air temp module is simply a fancy packaged resistor made for people who don’t know any better. Companies like SLP offer this for around $25, and many are lured into purchase by its low price and ease of install. It tricks your PCM into thinking it’s cold outside and therefore “optimizes timing”. In reality it does little to nothing and cannot change commanded timing by more than 1 degree (and that’s on a hot day where you probably can’t use the extra 1 degree of timing anyway). Save your money and don’t buy it. If your curiosity gets the best of you, buy an 8k resistor from Radio shack and save $24.50.

 Adjustable Fuel Pressure Regulator

On many boosted cars, fuel pressure needs to be raised as boost is added to compensate for extra air. The Grand Prix uses 2 methods to control fueling which render an AFPR worthless. The MAF sensor on the car reads the airflow and tells the PCM how much air is coming in and therefore how much fuel to deliver. As you mod and increase flow, the MAF reads more and increases fuel. The stock FPR changes fuel pressure with boost. As your boost increases, so does your fuel pressure. By changing this function by replacing the factory regulator you make your car impossible to tune. Adding fuel pressure doesn’t change the maximum pressure because your stock pump is limited to low 60’s in psi. So even though you might add 5 pounds at idle and cruising, you’re not adding that much at WOT. This makes tuning the car a nightmare. All the ZZP cars run stock regulators. If you have an aftermarket unit on your car, sell it and go back to stock. You can thank us later.

TPS Enhancer

If you want to increase throttle response, upgrade your PCM or buy other mods. The TPSE is an electronic gimmick that’s not worth the money.

Walbro fuel pump

If you have an M90 on your car, then your stock pump is capable of flowing enough fuel. Our 97 GTP put down 410WHP using a stock pump and our 2000 Monte Carlo (L36 200HP stock engine) put down 387WHP with the stock pump. Changing your fuel pump increases the chance of pump failure or problems due to hoses coming off so until you plan on making over 400WHP, keep the stock pump.

AutoTrans Interceptor

The trans interceptor is an electronic device that plugs in line with your transmission. It is supposed to improve transmission performance. You’re better off doing the job properly with a reprogrammed PCM.


With promises of increased gas mileage and HP, the Tornado is a total scam. It does nearly nothing and we have dyno tested it on a Dyno jet chassis dyno and it displayed a .5 HP loss.

Electric superchargers

Forget about it. Our supercharger dyno struggles to power an M90. The motor we use weighs about 400 pounds and draws 100,000 watts. That’s the equivalent of nearly dead shorting 10 Optima batteries in parallel! Do you really think a 120 watt fan is going to do anything? No. The only thing it will do is restrict the airflow your engine is trying to draw in.

Casper’s voltage booster

This is a lot of money for something that can be done for cheap!  Besides that, who needs brighter headlights and a faster warming seat heater when you have the car floored? No one, but that’s the only time the kit does anything!

By installing a 1 amp diode in the orange 12 volt reference wire you can raise your system voltage for a fraction of the cost. See our free mod on raising voltage.

Think you’ll get better ignition performance? Think again. The factory coil pack is internally regulated for a maximum 14.4 volts. Raising the system voltage a little via alternator rewire is helpful but beyond that the ignition system will not benefit.

Cryogenic Intercooler systems

These are systems that cool intake air or intercooler heat exchangers with CO2 gas. These offer extremely minimal airflow gains from the cooling and very large HP losses from the CO2 that is injected into the engine. Even the smallest amount of non flamable CO2 gas will cause a loss in HP. The added weight of the system slows the car down more than the 1-2 potential HP gained from cooling the intake air. On the dyno, we tested a unit on Tim’s 400whp turbo car and lost 40whp.