# How much can car performance be increased by performance shops and how do they do it? **URL:** \ **Category:** Factual Questions\ **Created:** [December 29, 2013, 8:33pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433 "2013-12-29T20:33:00Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Throatwarbler\_Mangrove](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@Throatwarbler\_Mangrove](https://boards.straightdope.com/u/Throatwarbler_Mangrove)\ **Post date:** [December 31, 2013, 1:46am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/21 "2013-12-31T01:46:09Z")
> [@FordTaurusSHO94](#): > > 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 twin screw supercharger is an entirely different type of device than a Roots type supercharger. ---
**Author:** ![Truman\_Burbank](https://avatars.discourse-cdn.com/v4/letter/t/ecc23a/32.png) [@Truman\_Burbank](https://boards.straightdope.com/u/Truman_Burbank)\ **Post date:** [December 31, 2013, 5:45am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/22 "2013-12-31T05:45:18Z")
and some of you guys clearly are. Short version of why no-one has mentioned nitrous? ---
**Author:** ![FordTaurusSHO94](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@FordTaurusSHO94](https://boards.straightdope.com/u/FordTaurusSHO94)\ **Post date:** [December 31, 2013, 6:41am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/23 "2013-12-31T06:41:39Z")
> [@Throatwarbler\_Mangrove](#): > > A twin screw supercharger is an entirely different type of device than a Roots type supercharger. You’re right, I was rambling. Other than riding in them, I have little experience with nitrous so I can’t answer that. ---
**Author:** ![epbrown01](https://avatars.discourse-cdn.com/v4/letter/e/7ba0ec/32.png) [@epbrown01](https://boards.straightdope.com/u/epbrown01)\ **Post date:** [December 31, 2013, 10:03am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/24 "2013-12-31T10:03:17Z")
> [@Truman\_Burbank](#): > > and some of you guys clearly are. Short version of why no-one has mentioned nitrous? NOS is like political power - those most likely to seek it are those least suited for it. After the first _The Fast and The Furious_, tons of kids bought kits and destroyed their engines and cars, leading to NOS getting a bad rep almost as quickly as it got popular. It’s not bad per se, but if you’re not racing it’s not a lot of use - it’s a complex, expensive system added to give you less than minute of extra power (depending on the size of tank you’re using); for day-to-day driving, supercharging and turbocharging make more sense. ---
**Author:** ![kferr](https://avatars.discourse-cdn.com/v4/letter/k/71e660/32.png) [@kferr](https://boards.straightdope.com/u/kferr)\ **Post date:** [December 31, 2013, 11:25am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/25 "2013-12-31T11:25:20Z")
> [@Lazlo Hapsburg](#): > > 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? Another reason for not maxing out the performance is that it allows manufacturers to use the same engines in different model cars with different performance/efficiency requirements. An example that I’m familiar with is the BMW 1 series diesels. The 118d, 120d, and 125d all use the same basic engine, but are tuned to 143, 184, and 218 bhp respectively. Starting prices range from £21,700 for the 118d to £27,500 for the 125d. ---
**Author:** ![Truman\_Burbank](https://avatars.discourse-cdn.com/v4/letter/t/ecc23a/32.png) [@Truman\_Burbank](https://boards.straightdope.com/u/Truman_Burbank)\ **Post date:** [December 31, 2013, 3:29pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/26 "2013-12-31T15:29:40Z")
> [@epbrown01](#): > > NOS is like political power - those most likely to seek it are those least suited for it. After the first _The Fast and The Furious_, tons of kids bought kits and destroyed their engines and cars, leading to NOS getting a bad rep almost as quickly as it got popular. > > It’s not bad per se, but if you’re not racing it’s not a lot of use - it’s a complex, expensive system added to give you less than minute of extra power (depending on the size of tank you’re using); for day-to-day driving, supercharging and turbocharging make more sense. Thanks for the info, my ignorance is being erased in little chunks. Sadly, my memory for details is leaving me at a somewhat higher rate… ---
**Author:** ![SanDiegoTim](https://avatars.discourse-cdn.com/v4/letter/s/85e7bf/32.png) [@SanDiegoTim](https://boards.straightdope.com/u/SanDiegoTim)\ **Post date:** [December 31, 2013, 6:26pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/27 "2013-12-31T18:26:01Z")
W/regard to nitrous, I disagree somewhat with the cost/complexity. A smaller (100-150 HP) kit isn’t all that expensive and not difficult to install, at least on carbureted engines. If installed/operated properly (to include timing retard) the risk of engine damage can be mitigated. For street/everyday use, however, it’s not a practical way to go. Primarily because NO2 systems are design only for wide open throttle usage, and there aren’t many opportunities during normal street driving to go to WOT. Less than WOT usage will trash the engine. Unlike mechanical power adders (superchargers & turbos), the power isn’t available all the time. It’s a hoot at the dragstrip, however. ---
**Author:** ![epbrown01](https://avatars.discourse-cdn.com/v4/letter/e/7ba0ec/32.png) [@epbrown01](https://boards.straightdope.com/u/epbrown01)\ **Post date:** [December 31, 2013, 7:24pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/28 "2013-12-31T19:24:17Z")
> [@SanDiegoTim](#): > > W/regard to nitrous, I disagree somewhat with the cost/complexity. A smaller (100-150 HP) kit isn’t all that expensive and not difficult to install, at least on carbureted engines. Ah, true enough - I forgot all about that. As you write, nitrous is great for drag racing, where carbs still seem to be king. ---
**Author:** ![FordTaurusSHO94](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@FordTaurusSHO94](https://boards.straightdope.com/u/FordTaurusSHO94)\ **Post date:** [December 31, 2013, 7:33pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/29 "2013-12-31T19:33:41Z")
To add to the above, with nitrous you need a Wide Open Throttle (WOT) switch and a window switch. You only want to spray when the engine is moving fast, otherwise it can puddle in the intake and cause a backfire. A nitrous backfire usually shatters modern plastic intake manifolds. The window switch limits the RPM range that the nitrous solenoid is active. You don’t want it to spray too early, because it will puddle, and you don’t want to it spray too high, because a lot of rev limiters work by cutting fuel. Nitrous adds a lot more oxygen into the engine, so you have to compensate by adding more fuel. If the fuel is cut while the nitrous is spraying, your engine goes lean and burns up quick. I’m not sure about carbed cars, but modern EFI cars usually use a wet kit or a dry kit. There may be more options, but I’m not real familiar with nitrous. A wet kit uses separate jets in the intake for the nitrous and additional fuel. A dry kit only sprays nitrous into the intake. You add more fuel by getting bigger fuel injectors and maybe a bigger fuel pump. You might also have to get a bigger fuel pump for a wet kit. You usually have to do it when you install a blower or a turbo though. My Cobra had a larger pump installed in the tank and then a secondary external pump in-line. ETA: I know a little more about nitrous than I mentioned in my previous post, but I’ve never personally installed or used it. I probably know enough to tell you how to blow up your car, ha! ---
**Author:** ![Clipper222](https://avatars.discourse-cdn.com/v4/letter/c/97f17d/32.png) [@Clipper222](https://boards.straightdope.com/u/Clipper222)\ **Post date:** [December 31, 2013, 7:46pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/30 "2013-12-31T19:46:31Z")
What kind of car is it that you’re thinking about modifying? Knowing that may allow folks to give you the most pertinent advice. ---
**Author:** ![epbrown01](https://avatars.discourse-cdn.com/v4/letter/e/7ba0ec/32.png) [@epbrown01](https://boards.straightdope.com/u/epbrown01)\ **Post date:** [December 31, 2013, 8:01pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/31 "2013-12-31T20:01:24Z")
> [@Clipper222](#): > > What kind of car is it that you’re thinking about modifying? Knowing that may allow folks to give you the most pertinent advice. I had the impression the OP was asking out of general curiosity rather than planning some upgrades. ---
**Author:** ![Ionizer](https://avatars.discourse-cdn.com/v4/letter/i/5daacb/32.png) [@Ionizer](https://boards.straightdope.com/u/Ionizer)\ **Post date:** [December 31, 2013, 8:11pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/32 "2013-12-31T20:11:26Z")
> [@Shagnasty](#): > > 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. I have to say the above is VERY wrong. I have ridden in/driven lots of 60-early 70’s Mopars (mostly 'Cudas and Chargers) and most of those _easily_ got into the 7’s and even a few very-low 6-second cars. Most of them were supercharged or twin-turbo’d with the blocks bored for more cubic-inch displacement (no replacement for displacement, as the saying goes). Only one of the cars had a protrusion from hood (tall supercharger) and every one of them were driven to track, ie street legal. I rode in one 7-sec Charger for about 250 highway miles to a show in Kansas, but it was loud (!!!) from the exhaust, but rode nicely otherwise. At the show, we put the slicks on to play, but used regular rubber for street driving of course. Something that REALLY makes a difference in older vehicles is the porting the heads for better/smoother airflow. I got about 45 more horsepower in my mostly OEM '71 Charger (punched out to around 400ci from the stock 383ci OEM size) by buying a plane ticket for an online buddy to visit and he hand-ported (with a grinder) my stock iron heads. Stunning improvement with simple removal of ‘airflow impdiments’ - he made airfoils out of particular areas and won a large bet (couple hundred dollars, IIRC) with the manager of the shop that ran the airflow test(s) before and after grinding of heads. Manager was pretty firm that there would be no way to improve the stock iron heads, LOL. The manager tried to hire him right there after the post-grinding airflow test, LOL! Too bad my friend was Canadian and had no way to work legally in USA. Anyways, the way to improve performance is to do whatever possible to allow more air to flow in and also get the exhaust flow as fast as possible (large and/or ‘open’ exhausts do not always equal faster times usually, gotta have the suction to pull fuel-mix into the bores, so to speak). Using non-OEM cams that allow more air flow at higher rpm’s helps a lot, but can make the engine idle rough due to how the valves are timed to open/overlap. Superchargers and turbos both cram more air in engine so more power can be made, but turbos can lag a bit hence twin-turbo setups with each set a bit different. At least that’s how my buddy had his set in his 'Cuda - a low-rpm unit and one for further into the powerband. That car looked, sounded, and drove exactly like stock (when driven gently), but push the pedal a bit, and front end/wheels would lift off ground; quite fun to pull wheelies when viewers have no idea or indications of the actual power under the hood 😉 The fastest I eer got my Charger at a track was just under 12 secs, but a lot more street-legal power could be had if I had chosen to go turbo and change the gearing on rear end. As it was ,I could travel at 70-80 mph without engine going much above idle; the torque engine made at low rpm’s was _great_. I also got over 30mpg highway, not too shabby imho 🙂 ---
**Author:** ![FordTaurusSHO94](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@FordTaurusSHO94](https://boards.straightdope.com/u/FordTaurusSHO94)\ **Post date:** [December 31, 2013, 8:59pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/33 "2013-12-31T20:59:20Z")
> [@Ionizer](#): > > I have to say the above is VERY wrong. I have ridden in/driven lots of 60-early 70’s Mopars (mostly 'Cudas and Chargers) and most of those _easily_ got into the 7’s and even a few very-low 6-second cars. Was this a particular bracket or class that put you around so many cars? To run those times, you pretty much have to have a full cage and all kinds of safety stuff and you’re getting out of the realm of what I call “easy.” ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [December 31, 2013, 9:25pm UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/34 "2013-12-31T21:25:37Z")
From time reading classic car magazines on the loo, I seem to remember engine blueprinting is a technique, an engine is taken apart and put back together again in such a way that any manufacturing defects are taken care of. ---
**Author:** ![epbrown01](https://avatars.discourse-cdn.com/v4/letter/e/7ba0ec/32.png) [@epbrown01](https://boards.straightdope.com/u/epbrown01)\ **Post date:** [January 1, 2014, 4:19am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/35 "2014-01-01T04:19:19Z")
Blueprinting is still done, but now typically done with upgraded parts, as stock engines are built to much better tolerances than the heyday of muscle cars. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [January 1, 2014, 4:24am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/36 "2014-01-01T04:24:15Z")
> [@Ionizer](#): > > I have to say the above is VERY wrong. I have ridden in/driven lots of 60-early 70’s Mopars (mostly 'Cudas and Chargers) and most of those _easily_ got into the 7’s and even a few very-low 6-second cars. Most of them were supercharged or twin-turbo’d with the blocks bored for more cubic-inch displacement (no replacement for displacement, as the saying goes). Only one of the cars had a protrusion from hood (tall supercharger) and every one of them were driven to track, ie street legal. I rode in one 7-sec Charger for about 250 highway miles to a show in Kansas, but it was loud (!!!) from the exhaust, but rode nicely otherwise. At the show, we put the slicks on to play, but used regular rubber for street driving of course. > > Something that REALLY makes a difference in older vehicles is the porting the heads for better/smoother airflow. I got about 45 more horsepower in my mostly OEM '71 Charger (punched out to around 400ci from the stock 383ci OEM size) by buying a plane ticket for an online buddy to visit and he hand-ported (with a grinder) my stock iron heads. Stunning improvement with simple removal of ‘airflow impdiments’ - he made airfoils out of particular areas and won a large bet (couple hundred dollars, IIRC) with the manager of the shop that ran the airflow test(s) before and after grinding of heads. Manager was pretty firm that there would be no way to improve the stock iron heads, LOL. The manager tried to hire him right there after the post-grinding airflow test, LOL! Too bad my friend was Canadian and had no way to work legally in USA. > > Anyways, the way to improve performance is to do whatever possible to allow more air to flow in and also get the exhaust flow as fast as possible (large and/or ‘open’ exhausts do not always equal faster times usually, gotta have the suction to pull fuel-mix into the bores, so to speak). Using non-OEM cams that allow more air flow at higher rpm’s helps a lot, but can make the engine idle rough due to how the valves are timed to open/overlap. Superchargers and turbos both cram more air in engine so more power can be made, but turbos can lag a bit hence twin-turbo setups with each set a bit different. At least that’s how my buddy had his set in his 'Cuda - a low-rpm unit and one for further into the powerband. That car looked, sounded, and drove exactly like stock (when driven gently), but push the pedal a bit, and front end/wheels would lift off ground; quite fun to pull wheelies when viewers have no idea or indications of the actual power under the hood 😉 > > The fastest I eer got my Charger at a track was just under 12 secs, but a lot more street-legal power could be had if I had chosen to go turbo and change the gearing on rear end. As it was ,_ **I could travel at 70-80 mph without engine going much above idle; the torque engine made at low rpm’s was great. I also got over 30mpg highway, not too shabby** _ imho 🙂 (bolding mine) Impressive, to say the least. 🆒 ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [January 1, 2014, 5:13am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/37 "2014-01-01T05:13:44Z")
> [@JBDivmstr](#): > > (bolding mine) > > Impressive, to say the least. 🆒 I know. It is incredible in the true sense of the word. We have multiple 60’s and 70’s era muscle cars that can do a quarter mile time well past any known world record while also being street legal and getting 30 miles per gallon on the road. I think we have an engineering record here. All we need to so is team him up with some of our other Dopers that have an IQ over 200 and I think we can all invest in the sure-fire company and be rich in short order. We can all do that _easily_. ---
**Author:** ![JBDivmstr](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@JBDivmstr](https://boards.straightdope.com/u/JBDivmstr)\ **Post date:** [January 1, 2014, 5:27am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/38 "2014-01-01T05:27:59Z")
> [@Shagnasty](#): > > I know. It is incredible in the true sense of the word. We have multiple 60’s and 70’s era muscle cars that can do a quarter mile time well past any known world record while also being street legal and getting 30 miles per gallon on the road. I think we have an engineering record here. All we need to so is team him up with some of our other Dopers that have an IQ over 200 and I think we can all invest in the sure-fire company and be rich in short order. We can all do that _easily_. Hmmm… Should that post have a :rolleyes: tacked on to the end of it? 😕;)😛 And here’s wishing everyone at the ‘Dope’ a Happy, prosperous, and safe New Year! 🙂 ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [January 1, 2014, 5:59am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/39 "2014-01-01T05:59:13Z")
> [@Lazlo Hapsburg](#): > > 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? you can boost the turbocharger limit with a $5 bleed valve and a supercharger with a different diameter drive wheel for very little money. The computer needs to be in on your hotrodding plans and reprogrammed to take advantage of it. ---
**Author:** ![FordTaurusSHO94](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@FordTaurusSHO94](https://boards.straightdope.com/u/FordTaurusSHO94)\ **Post date:** [January 1, 2014, 6:56am UTC](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433/40 "2014-01-01T06:56:28Z")
> [@JBDivmstr](#): > > Hmmm… Should that post have a :rolleyes: tacked on to the end of it? 😕;)😛 He’s wondering how a 1500 hp car that runs 6’s “easily” like [these](http://en.wikipedia.org/wiki/Pro_Stock) can also manage to get the same mileage as a modern Corvette with a quarter of the hp and modern aero. [Previous page](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433.md?page=1) [Next page](https://boards.straightdope.com/t/how-much-can-car-performance-be-increased-by-performance-shops-and-how-do-they-do-it/677433.md?page=3)