How much can car performance be increased by performance shops and how do they do it?

Many years ago (around 1978) I had a friend who bought a Chevelle with a 454 cubic inch engine and he took it to a performance shop to have them increase the performance. As a result, he was able to run the quarter mile in about 7 seconds.

I’d like to know just how much the performance of a stock car can be increased today and how that would be accomplished. By “performance” I mean mostly the acceleration - 0 to 60. But I’d also like to know about improving the handling in general ways (mostly the suspension) - meaning how to make the car corner well.

I’d like to know what modifications would have the greatest impact. I’m guessing that carburation would probably be the single biggest source for improvements to acceleration. Also, improving the manifolds (both intake and exhaust) would likely make a big difference.

But mostly, I’d like to know about turbo charging. I have heard several stories about how some people managed to hook up multiple turbo chargers. How much of an improvement is one turb charger vs two vs three? Would two turbo chargers come close to producing double the performance increase that a single one does?

Once I met this man at a drag strip one day who had a stock Camaro whose performance was mind-blowing fast. I asked him if he wouldn’t mind telling me how I could achieve the biggest increase in performance in a stock car and he answered, “Carburation”. I seem to recall he had installed one or more turbo chargers and he ran the quarter mile in times close to 8 seconds (with a mostly stock car). Maybe I’m mistaken about the turbo chargers. If it was a stock car, I guess it couldn’t have any turbo chargers installed.
Before posting this thread I did a search for “car performance” (without any quotes) and it turned up 20 pages but none of the entries seemed to have much of anything to do with car performance. When I searched for “car performance” (with the quotes), it returned 3 pages but few of them appeared to be about “car performance”. I did get a laugh from this one entry titled, “Mac or PC. You make the call”. I guess the quotes mean it has to find the exact search term. But I can’t understand why so few relevent entries were found when I searched for “car performance”. I really don’t want to turn this thread into a discussion about the search facility. But if you have any suggestions … well … I’ll leave it up to you. If you think it would be better to send me a private message than posting in this thread, that would be fine with me.

You might want to recheck those quarter mile times for his Chevelle and for the later ones that you note. Seven seconds isn’t even remotely plausible. No street legal car can run a quarter mile anywhere near that fast. A Chevelle is doing well if it can run one in 13 - 14 second range.

The fastest quarter mile time for any street legal car is a McLaren P1 at 9.8 seconds. As a rule of thumb, any time anyone claims a quarter mile time under 12 seconds for any 70’s muscle car, it is not true no matter how many performance modifications it has.

Drag racers are like fisherman. Their car is a minnow that grows to be a world record within three tellings of the story.

I’m sorry. You are correct. I don’t know why I remembered the times that way. The only reason I can think of was that it was avery long time ago. (1978 was 35 years ago).

There are as many different opinions about this as there are options. You can improve performance,handling, braking,etc… in a number of different ways, really the biggest factors are what end result you want specifically and, how deep your pockets are.

No. That is (presumably) the fastest time for a production street legal car. This car, for instance, runs 6.4 s and claims to be street legal.

I’m not aware of any legal upper limit (at least in the US) to engine size, turbocharging, etc. Street legal cars must meet minimum standards for headlights, seatbelts, and other things that don’t have much to do with quarter mile times other than adding a bit of weight.

Tires, mufflers, and emission control systems are probably the big items that need to change, but these are “bolt-on” items. There’s a bit of wiggle room here.

This is a big topic overall and it depends on the model and era of car that you start with. With some of the newish sports cars and performance sedans, the best bang for your buck is to swap the powertrain controller chip from the stock model to one that uses a more performance based strategy. That is an electronic hack that may void your warranty and will affect fuel economy and maybe engine life but it will give you faster performance and barely even require you to get your hands dirty. Those types of modifications are popular with models like the BMW M5.

It is an interesting question. There isn’t as much a garage mechanic can do today to significantly enhance performance on most modern vehicles unless you resort to something extreme like turbocharging a car that wasn’t designed for it. On the other hand, 60’s and 70’s era muscle cars weren’t nearly as fast as most people remember them either. My stock Toyota Rav4 sport (a family hauler small SUV) can blow the vast majority of them ever made away without breaking a sweat.

Below is an interesting older thread that should give you an idea of the limitations that older hot-rodders tried to find solutions for. Most of those issues aren’t nearly as big a factor for newer models of cars. Tire technology alone is infinitely better than it was 40 years ago and that is just one area that has seen drastic improvement.

Muscle Car Shootout: Would today’s fastest cars shut down the '60s-'70s muscle cars?

Performance in modern cars is tweaked with computers. Dyno Tuning.

Any performance shop will have a lot invested in their equipment.


Thanks for posting that older thread.

It was fascinating to read about the differences between modern cars and the older muscle cars from the 70s.

I can see that I’m going to need to re-think my entire position on this.

As the saying goes “Speed costs money - how fast can you afford to go?”

The most typical performance upgrade nowadays - and the cheapest - is ECU tuning. Th next step is freeing up the engine’s breathing with an aftermarket air filter and intake and free flowing exhaust. After that, you typically do cams and/or headers, maybe bigger injectors. You can spend about three or four grand on all this for a Euro car and add maybe 10% horsepower.

The next step (and better bang for the buck) is typically forced induction using supercharging or turbocharging, which runs a few grand but it much more tune-able and can bump power by 30% or more. At this point, you’re going to want improve the suspension and brakes as well. The good news is if your car is already turbocharged or supercharged, simple ECU tuning can give you big performance gains, and you can get even more by upgrading the existing components. (Google Juicebox.)

After that - and this was typical of muscle cars - you can crack the engine open and upgrade the internals - pistons, cams, crank - in addition to header, carbs, intakes, etc. The parts are readily available, fairly inexpensive, pretty reliable. You can also just swap in a built engine from a tuner for just a few grand. That sort of thing on a Porsche, Mercedes-Benz AMG or BMW ///M can run you $20k - the expense is a large part of why BMW and MB have their own tuning divisions.

Two of the top US tuners for modern performance cars. Just bring money:D

The short answer as to how much performance can be squeezed out of a particular vehicle relates to money. Specifically, how much you have to spend. As someone who has owned, modified and drag raced American muscle cars since the mid sixties, I can tell you that in the street legal world, there’s more performance to be had with today’s performance cars than with my favorites of the mid/late 1960’s. However, IMHO the original muscle cars has more personality. Obviously, I’m no spring chicken.

You upgrade modern cars the same way you upgrade older cars. The big difference is that you tune them with a laptop instead of a screw driver. It’s not a black art either, I’ve got several friends that can tune cars. A popular option for GM vehicles is HP Tuners. Once you buy the hardware and software, you can tune vehicles. Most of my friends charge $100-200 for a car. A dyno makes it a lot easier, but you can use a wide-band and just run it down the road.

Most cars pick up a little bit from a tune. Automatics can see a slightly bigger jump because you can change the shifting up a little.

However, if you want acceleration, low gears, sticky tires, and maybe lower control arms (if it’s a solid axle) or a poly bushing kit (if IRS) will give you a lot more of a kick in the pants and a drop in 60’ times or 0-60 times, whatever you’re after. Depending on the car, you may also want to stiffen the chassis a bit with weld-in subframe connectors.

The next thing I would do is forced induction. A roots blower if you want instant torque, a centrifugal blower if you want a top end charge, or a turbo if you want be able to fine tune the powerband. You can make a supercharger work kind of like a turbo by converting it to a blow through set up, but that’s not a common set up. Single or twin turbo is up to you. Most people seem to convert twin turbo Supras into a big single, but other people convert some things to twins. It depends on what you’re after.

There’s no single specific way to get speed, but none of it is cheap. Also, street legal and streetable are two different things. You can have a 25 second beater that’s not street legal, but have a 6 second car that is. How fast or powerful something is has nothing to do with it being street legal, that’s a movie term.


Wow! I have never even heard of some of the blowers and turbochargers to which you referred.

I did look up “Roots Blower” and found the following (in case anyone else is interested):

The Roots type supercharger or Roots blower is a positive displacement lobe pump which operates by pumping a fluid with a pair of meshing lobes not unlike a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust. It is frequently used as a supercharger in engines, where it is driven directly from the engine’s crankshaft via a belt or, in a two-stroke diesel engine, by spur gears.

I wonder why I have never heard of “Roots Blower” before.

Oh well, it certainly will give me some good reading over the New Years Holiday.

Thanks very much!


I have never hear of those tuners before either.

Very interesting. I can see I will be having some nice dreams about ways to spend my retirement money. I was gonna leave it to my grandkids. But they are a real bunch of snots. One of them even told me to “fuck off” the other day. I think I will send him a message in the reading of my will. Just not sure as to the best way to do that. Maybe I will leave him some photocopy evidence of my cashing in the bonds I was gonna leave him and the receipts I got from the tuner where I spent the money. I could just conclude by telling him that I leave him a big “fuck you too”. Heh. Heh.

Very informative post.

But one thing I don’t understand is, if the car is already turbocharged or supercharged, why would it not already have been ECU tuned to give those big performance gains? What would be the point in turbocharging or supercharging if the potential for big performance gains was left untapped?

Engine lifetime, mostly. Plus some emission issues, ease of driveability (you don’t want to burn rubber every time you step on the gas*), etc.

There’s an ideal ratio of air to gasoline vapor for optimum power- roughly 14.7:1. Getting more gas in there is easier - just open the fuel injectors for a longer interval, or if that still doesn’t provide enough gas, switch to higher-flow injectors. Managing air is more difficult, since we don’t have a tank of it under pressure, but have to pull it in from outside the car.

Where do we get that extra air? We have to pump it ourselves. A supercharger compresses air using power taken directly from the engine drivetrain, via a pully and belt. A turbocharger gets its power from the flow of exhaust gas. Which is better? Depends on what you want to achieve. In either case, the end result is more air + more gas in the same size engine = bigger boom = higher performance = more engine wear.

The factory selected the engine components based on the amount of power their standard tune produces. Creating lots of extra power requires upgraded internals if you want the engine to last. For the 20-30HP you’ll get from fiddling with the ECU and headers, it isn’t that important.

To give you an idea, here is a list of what needs to be done to take a 205HP 2.0L GM LSJ engine to 1400HP.

  • Yes, it can happen - I can easily burn rubber in any gear up to and including 4th.

A stock vehicle is legally required to comply with emissiosn regulations, and the manufacturer also has durability requirements; they don’t want to sell cars that aren’t going to outlive the warranty. additionally, the manufacturer has driveability requirements: they don’t want to sell a car that barely idles, which means they compromise performance everywhere else (engines that are extremely optimized for power/torque tend to idle like crap).

Once you buy it, you are no longer burdened by those restrictions. Well, strictly speaking, you’re supposed to comply with emissions laws, but if you don’t live in a state with a smog check, nobody’s going to call you on it. You are free to run it as rich/dirty as you want, and if you’re OK with the risk of the pistons holing on your next 1/4-mile run, that’s entirely up to you.

They are the only kind of superchargers I’ve ever seen on factory supercharged engines. They go by several names though: roots, positive displacement, twin screw, etc.

My last Cobra had a centrifugal blower and the engine felt stock until about 3500-4000 RPM. After that, it had a massive top end charge all the way to about 6800 RPM. It felt like a 2-stroke engine. It was completely docile below that though. Of course, I fixed that by putting 4.10 gears and drag radials on the car though, ha!

A big part of the answer is that in the old days engines were mostly designed to be cheap to manufacture.

Many of the cost saving features tended to limit rpm, or to impair airflow at higher rpm, causing torque and thus power to fall as the tach climbed.

By making changes that allowed the engine to maintain torque at higher rpm, you could boost the power in proportion to the new redline. This would include a higher flow carb, port work, a better or modified intake manifold, lightweight forged pistons and rods, a long duration/high lift cam, and exhaust headers. Then you need an upgraded ignition system that will work at the new higher compression ratio ( forgot to mention that) and high redline. Now change the accessory pulleys so things only run just fast enough to work most of the time . At
that point, if you didn’t screw up (as many would have) you might see a 50% or so improvement in power…maybe a little more.

Most of that gain (exhaust excepted) and more, already happens at the factory these days. The best performance carburetors were not equal to average factory EFI, and many engines have factory redlines that muscle car era dragracers didn’t even bother to dream of. You get 4-5 valves/cylinder, overhead cams, aluminum intakes, electronic ignition, and maybe even variable valve timing (V-tec) and staged intake tuning right off the showroom floor.

This (10.21 second in the 1/4 mile) ‘farm truck’, is purportedly street legal. :smiley: