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Let's Talk Horsepower

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165
CA
Question for the group:



How much do you think horsepower matters, all other factors being equal? It’s a long shot, but do any of you have before and after lap time data where all you did was increase (or decrease) your HP?

I find myself at a bit of a wall with my car. As it sits, I have 285whp, 290wtq, low, for a 3v mustang given my mods, and especially low for a ~3600lb car. That puts me at a rather abysmal power to weight ratio of .0792 hp/lb…For reference, a typical S2000 HPDE build is 0.088 HP/lb.

Relatively speaking, I put down great lap times with my car, but in the back of my head it absolutely kills me that I have such a lack of “oomph” in the straits. S2000’s, BRZ’s, newer miatas, etc. have to let off when they give me point by’s. Everyone is surprised when they learn how little horsepower my car has.

Naturally being my curious self, I have started to look into power mods for my car. For about $1600, I can put a set of no springs required cams and an electric water pump in the car, which should bring me up to about 315whp. But, I have no idea if +30whp will be anything worthwhile to really impact my lap times. Anyone have any insight?

Weight reduction is definitely on the list for me, but I just wanted to see if any of you have had some experience with adding ~30whp and seeing lap times change dramatically, or not at all.

Thanks everyone!
 

Mad Hatter

Gotta go Faster
4,865
3,718
Santiago, Chile
Oh, boy... Ye Olde hp debate! I had my car a a healthy 470rwhp and later upgraded to a new engine with 500+ rwhp. With the same suspension setup etc as before the car definitely got more competitive But not in immediate big drops to lap times.. it was more like in the ability to pass when you want too!

After a few track days I managed to drop my PB by 2 seconds and I expect I have one more as I get used to having the extra power. The one super feature I have in racing against Porsches etc, is that my engine puts out more torque then they do and still runs to 8000 rpm, I would sorely miss not having 400+ ft/lbs of torque to the wheels.

So if I was you, I would drop weight AND collect all the HP you can find. Would hate to race a BRZ that had the same power to weight ratio as I.
 

Dave_W

Cones - not just for ice cream
655
794
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
my engine puts out more torque then they do and still runs to 8000 rpm, I would sorely miss not having 400+ ft/lbs of torque to the wheels.
Everyone always talks about horsepower, but IMHO our friend south of the equator nails it here. Torque is what accelerates you out of the corner and down the straight, and your engine runs in a range of rpm from corner exit to the end of the straight. So you really need to determine the rpm range you'll see for the tracks you want to run (or guesstimate minimum rpm based on gear & apex mph and assume you'll run to redline). Then evaluate performance mods for improvements in the area under the torque curve in the desired rpm range. If all else is staying the same, adding 50HP at 6000rpm but making the engine "peakier" and losing torque from 3000 to 5000 may end up giving you slower lap times.

A number of years ago, the head of Audi North America said in an interview, "Americans buy horsepower, but they drive torque."
 

Mad Hatter

Gotta go Faster
4,865
3,718
Santiago, Chile
Following in the theme @Dave_W brought up. Putting in some hot cams that give you 30 whp more at the top, but it might not be worth losing bottom end. Otherwise those pesky miatas will really give you a hard time.

Thats whats so nice about the LM intake cams for the coyote... No torque loss at lower rpms but a nice hp bump at the top.
 
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I'm sure 30 hp would be a decent improvement provided you don't lose torque.

But if you really feel you are at a wall with lap times, and from looking at your build thread (awesome btw, good read), I think you would get more ROI from a set of GY 3R's or similar than you would from a cam and electric water pump. If the cam and water pump are part of other work you need to do then I probably would go for it. But as a standalone mod for lap times, I think I would look elsewhere first if that makes sense?

3600 lbs also seems a little heavy for your car, is that with you and a full tank of fuel?

If you have the time and budget, then just do it all of course!
 
I found myself asking myself a similar question at the end of this autocross season. At 3450lbs with maybe 265whp I could keep pace and beat a lot of higher hp cars on short courses, but on large course with multiple 2-3 shifts I was getting dusted.

Given the displacement limitations of the 3.7, I know I'll never be able to make anywhere near the power of the 5.0's especially in the newer s550's. So I decided to focus on the things I can control to maximize my chances: matching their tire size, weight reduction, and increasing usable power with breathing mods.

I haven't tested anything yet, but I'm hoping at 33xxlbs and closer to 300whp the car will be able to hang with faster company.
 

Bill Pemberton

0ld Ford Automotive Racing Terror
7,236
6,468
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
Old rule of thumb;
" For every 100 lbs lost , you gain 1 second on a 2 mile track."

Lose the weight as you pony is a little chubby, and then view some other simple bumps in power. Keep in mind, if you decide to run NASA Time Trials ( for instance ) , that the HP to weight ratio may put you in a better Class ( as in lower ) to compete, since the top Classes will have the HP and in many cases solid torque numbers too.

Good luck and there are so many ways to lose weight ( hoods, Optic Armor windshields, lighter batteries, two piece rotors, race sears , etc. ).
 
74
114
Exp. Type
Time Attack
Exp. Level
10-20 Years
75024
One data point, when I went from the 350 to the 500, there was a 44-45% hp/tq increase. Weight increased by 2%. Lap times at my home track, after lots of dialing in, on similar 200tw tires, and suspension, dropped by 4sec over a 2min 4-7s lap. Thats only a 3% improvement. Not the best ROI, but every bit counts. So a 10% improvement in power to weight, it might gain 3/4-1% in lap time in this scenario ?
 
One data point, when I went from the 350 to the 500, there was a 44-45% hp/tq increase. Weight increased by 2%. Lap times at my home track, after lots of dialing in, on similar 200tw tires, and suspension, dropped by 4sec over a 2min 4-7s lap. Thats only a 3% improvement. Not the best ROI, but every bit counts. So a 10% improvement in power to weight, it might gain 3/4-1% in lap time in this scenario ?

Super interesting. Appears to be the law of diminishing returns in effect. Or our pigs are just too heavy!
 
16
15
Exp. Type
HPDE
Exp. Level
Under 3 Years
SE Virginia
As it sits, I have 285whp, 290wtq, low, for a 3v mustang given my mods, and especially low for a ~3600lb car.
In your build thread you quote 313hp in one post, which I thought was okay for a 3v Mustang with some bolt-ons.
I was wondering why you say 285hp now, and then got to where you thought the valve seals (seats?) are going kaput.

If you fix that and get back to 310+ at the wheels, I think your power is doing alright. You're not gonna get much more with bolt-ons, are you?
In my (admittedly limited) experience I would expect a 10% increase in power to feel good in the driver's seat and hardly make any difference in lap times. That power difference is a drop in the bucket compared to what you've got for tires and suspension.
 
Last edited:
74
114
Exp. Type
Time Attack
Exp. Level
10-20 Years
75024
Super interesting. Appears to be the law of diminishing returns in effect. Or our pigs are just too heavy!
Yes, diminishing returns, as corner exit is still traction limited, so no big gains until you are straight. Then corner entry gets more spicy as entry speed has jumped 5-10mph everywhere. I have corner speeds now matching the 350, but still working on the rest.
 
175
165
CA
In your build thread you quote 313hp in one post, which I thought was okay for a 3v Mustang with some bolt-ons.
I was wondering why you say 285hp now, and then got to where you thought the valve seals (seats?) are going kaput.

If you fix that and get back to 310+ at the wheels, I think your power is doing alright. You're not gonna get much more with bolt-ons, are you?
In my (admittedly limited) experience I would expect a 10% increase in power to feel good in the driver's seat and hardly make any difference in lap times. That power difference is a drop in the bucket compared to what you've got for tires and suspension.
Great catch

That is the sad part...at one point my car but down 313whp...3 years later, I had it dyno'd and it put down 290whp with straight through exhaust. I then added the stock bullitt mufflers back to the car which likely puts me at about 285whp. Same dyno, similar weather, only thing different that would make the car read lower was it was on 285/35/19's when it

I think it's valve seals because the engine burns a lot of oil, and on decel, smells like oil. So somewhere somehow oil is going bye bye....A leak like that usually means a loss in compression and therefore power. This is all just speculation though.

This is why I'm pretty interested in getting some nice heads built, and then sticking some decent cams in them. I think it would fix my potential valve seal issue and also give me more power.

I looked into doing the valve seals myself, and it's just too much for me to tackle I think. Lot's and lots of labor.
 
Last edited:
175
165
CA
Old rule of thumb;
" For every 100 lbs lost , you gain 1 second on a 2 mile track."

Lose the weight as you pony is a little chubby, and then view some other simple bumps in power. Keep in mind, if you decide to run NASA Time Trials ( for instance ) , that the HP to weight ratio may put you in a better Class ( as in lower ) to compete, since the top Classes will have the HP and in many cases solid torque numbers too.

Good luck and there are so many ways to lose weight ( hoods, Optic Armor windshields, lighter batteries, two piece rotors, race sears , etc. ).
Love this rule of thumb.
One data point, when I went from the 350 to the 500, there was a 44-45% hp/tq increase. Weight increased by 2%. Lap times at my home track, after lots of dialing in, on similar 200tw tires, and suspension, dropped by 4sec over a 2min 4-7s lap. Thats only a 3% improvement. Not the best ROI, but every bit counts. So a 10% improvement in power to weight, it might gain 3/4-1% in lap time in this scenario ?
Not a great ROI but a great data point nonetheless!
I'm sure 30 hp would be a decent improvement provided you don't lose torque.

But if you really feel you are at a wall with lap times, and from looking at your build thread (awesome btw, good read), I think you would get more ROI from a set of GY 3R's or similar than you would from a cam and electric water pump. If the cam and water pump are part of other work you need to do then I probably would go for it. But as a standalone mod for lap times, I think I would look elsewhere first if that makes sense?

3600 lbs also seems a little heavy for your car, is that with you and a full tank of fuel?

If you have the time and budget, then just do it all of course!
My only issue with this is I want to keep the car "budget friendly", and after really sitting down and trying to figure out how to make the sport cheaper, I settled with the fact that I can't afford the super fast, super quick wearing tires. So I would rather make the car faster with things which are just an initial investment vs. a recurring cost.

Everyone always talks about horsepower, but IMHO our friend south of the equator nails it here. Torque is what accelerates you out of the corner and down the straight, and your engine runs in a range of rpm from corner exit to the end of the straight. So you really need to determine the rpm range you'll see for the tracks you want to run (or guesstimate minimum rpm based on gear & apex mph and assume you'll run to redline). Then evaluate performance mods for improvements in the area under the torque curve in the desired rpm range. If all else is staying the same, adding 50HP at 6000rpm but making the engine "peakier" and losing torque from 3000 to 5000 may end up giving you slower lap times.

A number of years ago, the head of Audi North America said in an interview, "Americans buy horsepower, but they drive torque."
This is why I'm pretty interested in cams tbh, as the stock 3v cams really tend to lose torque at around 5200RPM, whereas even cheap stage 1 cams keep the HP but most impressively torque really strong all the way up to ~65000 RPM. +40WTQ at around 5800RPM is not unheard of with mild cams on the 3v.
 
175
165
CA
I am working on an excel sheet calculator to calculate the best bang for the buck to increase the power to weight ratio, whether that be with HP or by losing weight.

I'm hoping to get the car to 01.HP/LB.

So for example, 320whp and 3200lbs. That would have to make a pretty huge difference in performance, no?
 
16
15
Exp. Type
HPDE
Exp. Level
Under 3 Years
SE Virginia
Great catch

That is the sad part...at one point my car but down 313whp...3 years later, I had it dyno'd and it put down 290whp with straight through exhaust. I then added the stock bullitt mufflers back to the car which likely puts me at about 285whp. Same dyno, similar weather, only thing different that would make the car read lower was it was on 285/35/19's when it

I think it's valve seals because the engine burns a lot of oil, and on decel, smells like oil. So somewhere somehow oil is going bye bye....A leak like that usually means a loss in compression and therefore power. This is all just speculation though.

This is why I'm pretty interested in getting some nice heads built, and then sticking some decent cams in them. I think it would fix my potential valve seal issue and also give me more power.

I looked into doing the valve seals myself, and it's just too much for me to tackle I think. Lot's and lots of labor.
Valve guide seals, around the valve stems? Changing them means taking practically everything off the head, doesn't it?
Then you might as well start comparing the price of that job with new aftermarket heads that will get you more power, and what cams you'd like on those heads.
Then, you start comparing the price of the head swap with the price of installing a low-mile Coyote... 🤔

That should make enough difference in power to improve your lap times. 😇
 
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165
CA
Valve guide seals, around the valve stems? Changing them means taking practically everything off the head, doesn't it?
Then you might as well start comparing the price of that job with new aftermarket heads that will get you more power, and what cams you'd like on those heads.
Then, you start comparing the price of the head swap with the price of installing a low-mile Coyote... 🤔

That should make enough difference in power to improve your lap times. 😇
Sorry, I believe it is the valve seals. The rubber viton ones which you can access once you remove the cams, springs, followers, retainers, etc.

These ones:
1670524817514.png

If it's the guides themselves, then I agree....Will be pricing out new heads most definitely


That's my issue, I have perpetual underdog syndrome, so I want to keep the 3V in the car to be "different", and to be able to say "it's just a 4.6, not a coyote" 🤣 🤣

Always need to have my excuses lined up for being slow....
 
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I am working on an excel sheet calculator to calculate the best bang for the buck to increase the power to weight ratio, whether that be with HP or by losing weight.

I'm hoping to get the car to 01.HP/LB.

So for example, 320whp and 3200lbs. That would have to make a pretty huge difference in performance, no?
Best bang for the buck is almost always going to be losing weight. First, it's often free depending on how much you are willing to live without. Second, for two cars with identical power to weight ratio, and everything else the same, the lighter car will be faster. Your car at 3000 lbs and 300 hp will be faster than 4000 lbs and 400 hp. Not sure how that gets reflected in your excel spreadsheet but you see the point....
 
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Untitled Spreadsheet
ModRWHP IncreaseRWHP/LBWeight Decrease (lbs.)Vehicle WeightRWHP/LB % IncreaseCost ($)$ Per % RWHP/LB Increase
Stock00.0814N/A3500000
NSR Cams250.0886N/A35008.85%1000113
VSR Cams400.0929N/A350014.13%2000142
Headers150.0857N/A35005.28%1500284
Electric Water Pump100.0843N/A35003.56%650183
Heads (No cams)400.0929N/A350014.13%3500248
Heads and Cams650.1N/A350022.85%7000306
Wiper MotorN/A0.0815334970.12%00
Wiper LinkageN/A0.0815434960.12%00
Wiper ArmsN/A0.08148234980%00
Wiper BladeN/A0.08140.6634990%00
A/C SystemN/A0.08244034601.23%00
Rear Seat HardwareN/A0.0815534950.12%00
MufflersN/A0.08171034900.37%00
AGM BatteryN/A0.08181534850.49%350714
Lithium BatteryN/A0.0822534750.74%650878
Girodisc RotorsN/A0.0822634740.74%21002,837
K-memberN/A0.08192034800.06%00
DriveshaftN/A0.08181634840.49%7001,428
Sound DeadeningN/A0.08181534850.49%00
HeadlinerN/A0.0816834920.25%00
CarpetN/A0.08181434860.49%00
Carbon Fiber FendersN/A0.0815434960.12%7506,250
Carbon Fiber TrunkN/A0.08192034800.61%7501,229
FRPP Tow Bar FrontN/A0.08168.43491.60.25%00
Radiator SupportN/A0.0815534950.12%2752,292
FRPP Tow Bar RearN/A0.0816734930.25%3751,500
Fender LinersN/A0.0816634940.25%00
Gutted DoorsN/A0.08327534252.21%00
Lexan Windows:N/A0.08223134690.98%11201,142
APEX VS-5RS (compared to flow formed 18x11 EC7)N/A0.081814.63485.50.49%35007,143
Center ConsoleN/A0.08181534850.49%00
HeadlinerN/A0.0815434960.12%00
 

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