*Another* JRSC review in combination with a full exhaust, daily driver

[glamcem]

Originally Posted by CSG Mike

A CARB JRSC will walk:

- Stock EVO
- Stock 350Z/370z
- Stock WRX/STI
- Stock Focus ST

It is about even with:

- bolted EVO on pump
- Flashed/bolted 370z
- fully bolted STI on pump
- Fully bolted ST
- E9x M3

It will lose to:

- Any factory FI car on E85
- F80

it's partially true Mike, I've driven/owned almost all the cars you mentioned above (except Focus ST ,or the E9X M3s).. roll from 30-40 mph you have some window to keep up with those cars but as soon as you shift the cars you mentioned will start walking away for multiple reasons:

• advantage of the power/weight ratio will diminish (talking about highway pulls of course) after certain speed say about after 70-80mph since after that HP will start make up for the difference and after 100mph more powerful car will almost always walk away (opposite can be said for the lighter cars at the tracks with tight corners, if we think about it; Lotus Elise doesn't really have a good Power/weight ratio compared to big dogs.. say for instance than a Challenger Hellcat, but it will possibly kill many of them on a tight/medium track since weight advantage overcomes the other disadvantages regardless of the power/weight ratio)
  
  
• gearing advantage in stock form slightly becomes a disadvantage with the added power, if the boosted BRZ/FRS makes more than 300whp having a slightly taller tires might be good way of cheating if taller gears is not an option
  
• OEM power (especially in NA form) is a lot healthier and more repeatable so after a couple of pulls car with an aftermarket FI kit will start losing power due to overheating (even with the best cooling methods), of course Rotrex kits still has the upper hand compared to turbo (since heat soak is not an issue like a turbo) on that department but still subject to the shortcomings I mentioned above

with all that said, with a proper cooling and supporting mods, Rotrex SC'd FRS/BRZ still has a huge advantage on a track but not proportionally with the power it makes on a dyno since real world power will suffer from..this is just another example of the power on paper and power on real world conditions

[ck-GT86]

Originally Posted by glamcem

it's partially true Mike, I've driven/owned almost all the cars you mentioned above (except Focus ST ,or the E9X M3s).. roll from 30-40 mph you have some window to keep up with those cars but as soon as you shift the cars you mentioned will start walking away for multiple reasons:

• advantage of the power/weight ratio will diminish (talking about highway pulls of course) after certain speed say about after 70-80mph since after that HP will start make up for the difference and after 100mph more powerful car will almost always walk away (opposite can be said for the lighter cars at the tracks with tight corners, if we think about it; Lotus Elise doesn't really have a good Power/weight ratio compared to big dogs.. say for instance than a Challenger Hellcat, but it will possibly kill many of them on a tight/medium track since weight advantage overcomes the other disadvantages regardless of the power/weight ratio)
  
  
• gearing advantage in stock form slightly becomes a disadvantage with the added power, if the boosted BRZ/FRS makes more than 300whp having a slightly taller tires might be good way of cheating if taller gears is not an option
  
• OEM power (especially in NA form) is a lot healthier and more repeatable so after a couple of pulls car with an aftermarket FI kit will start losing power due to overheating (even with the best cooling methods), of course Rotrex kits still has the upper hand compared to turbo (since heat soak is not an issue like a turbo) on that department but still subject to the shortcomings I mentioned above

with all that said, with a proper cooling and supporting mods, Rotrex SC'd FRS/BRZ still has a huge advantage on a track but not proportionally with the power it makes on a dyno since real world power will suffer from..this is just another example of the power on paper and power on real world conditions

Damnit....so what do I do now? Edelbrock, JRSC, or sell for an E92 M3 like was about to?

lol, thanks.

[glamcem]

Originally Posted by ck-GT86

Damnit....so what do I do now? Edelbrock, JRSC, or sell for an E92 M3 like was about to?

lol, thanks.

depends on your goals:

• if you're like me; appreciate almost every aspects of the the car (lighweight, lower center gravity, handling, practicality, mpg etc.. ) especially for having fun at track days but find it very boring due to lack of power, you're options are limited IMO, Rotrex based kits (JR or KW)
  
• if you like everything above but prefer more low end torque and not planning to attend track days as much (it would be a shame with this car IMHO) Cosworth Supercharger may be good option..then again it will generate a lot more heat at the track (thanks to a water intercooled system) and only handle mild track use and also not sure if it's worth the added cost
  
  
• if you like really fast car on highway, pulls, 1/4 mile ..etc (I am not saying quick car) you probably got the wrong car and your best bet is to consider other alternatives..

[glamcem]

@ck-GT86 keep in mind this general rule doesn't really change much:

"FAST - RELIABLE - CHEAP

pick two"

[CSG Mike]

Originally Posted by ck-GT86

Any preferred MAP sensor you recommend?

Thanks

Anything 2.3BAR or higher will work.

[CSG Mike]

Originally Posted by glamcem

it's partially true Mike, I've driven/owned almost all the cars you mentioned above (except Focus ST ,or the E9X M3s).. roll from 30-40 mph you have some window to keep up with those cars but as soon as you shift the cars you mentioned will start walking away for multiple reasons:

• advantage of the power/weight ratio will diminish (talking about highway pulls of course) after certain speed say about after 70-80mph since after that HP will start make up for the difference and after 100mph more powerful car will almost always walk away (opposite can be said for the lighter cars at the tracks with tight corners, if we think about it; Lotus Elise doesn't really have a good Power/weight ratio compared to big dogs.. say for instance than a Challenger Hellcat, but it will possibly kill many of them on a tight/medium track since weight advantage overcomes the other disadvantages regardless of the power/weight ratio)
  
  
• gearing advantage in stock form slightly becomes a disadvantage with the added power, if the boosted BRZ/FRS makes more than 300whp having a slightly taller tires might be good way of cheating if taller gears is not an option
  
• OEM power (especially in NA form) is a lot healthier and more repeatable so after a couple of pulls car with an aftermarket FI kit will start losing power due to overheating (even with the best cooling methods), of course Rotrex kits still has the upper hand compared to turbo (since heat soak is not an issue like a turbo) on that department but still subject to the shortcomings I mentioned above

with all that said, with a proper cooling and supporting mods, Rotrex SC'd FRS/BRZ still has a huge advantage on a track but not proportionally with the power it makes on a dyno since real world power will suffer from..this is just another example of the power on paper and power on real world conditions

- The FRS/BRZ has a smaller CdA than every car listed. The higher the speed, the larger the CdA advantage. The STI and Evo is a flying brick.

- Gearing is moot; tight gearing is better for the JRSC powerband anyways. It's not ilke you deal with turbo lag.

- Repeatability... is debateable, but none of the setups listed above will have issues repeating performance from a roll.

[ck-GT86]

Originally Posted by glamcem

depends on your goals:

• if you're like me; appreciate almost every aspects of the the car (lighweight, lower center gravity, handling, practicality, mpg etc.. ) especially for having fun at track days but find it very boring due to lack of power, you're options are limited IMO, Rotrex based kits (JR or KW)
  
• if you like everything above but prefer more low end torque and not planning to attend track days as much (it would be a shame with this car IMHO) Cosworth Supercharger may be good option..then again it will generate a lot more heat at the track (thanks to a water intercooled system) and only handle mild track use and also not sure if it's worth the added cost
  
  
• if you like really fast car on highway, pulls, 1/4 mile ..etc (I am not saying quick car) you probably got the wrong car and your best bet is to consider other alternatives..

I fall into the first two, with the exception to occasional track days. I hardly drive my car now as it is thanks to free public transportation, but I do find the power boring when I do.

.ck

[Jackson Racing]

@autograph -

Great to hear you like your Jackson Racing supercharger system! Yeah, open exhaust TIY kits are pretty loud. I still run a completely factory exhaust on my street FR-S.

There should be a good bump in power throughout, with it getting stronger as it heads towards redline. Think of it like a bigger engine being in the engine bay.

We have had quite a few customers order TIY kits then call and order the CARB calibration to improve their overall drivability. They drive a friends Factory Tuned system and notice it drives completely different. A proper ECU calibration is important to overall performance and drivability.

-Oscar Jr.

[shu5892001]

Originally Posted by ck-GT86

Damnit....so what do I do now? Edelbrock, JRSC, or sell for an E92 M3 like was about to?

lol, thanks.

beware of rod bearing issues if you plan to go that way lol

[ck-GT86]

Originally Posted by shu5892001

beware of rod bearing issues if you plan to go that way lol

Oh crud, I wasn't aware of those. I see you previously owned one!

.ck

[glamcem]

Originally Posted by CSG Mike

- The FRS/BRZ has a smaller CdA than every car listed. The higher the speed, the larger the CdA advantage. The STI and Evo is a flying brick.

yes Evo and STI has a slight disadvantage on drag coefficient figures (.27 vs .30X something) but that disadvantage becomes negligible especially when the speed increases ..see below formula:

A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula

- Gearing is moot; tight gearing is better for the JRSC powerband anyways. It's not ilke you deal with turbo lag.

I was referring to the highway pulls not the transient lag that is inherited in turbos, I should've said "better matched gears" because taller gears only have advantage for that specific power levels ..M3 with it's longer gears will almost always walk away from the SC'd FRS/BRZ with less than ~300whp

- Repeatability... is debateable, but none of the setups listed above will have issues repeating performance from a roll.

compared to other FI choices yes but compared to NA? well we know the answer

[CSG Mike]

I love wikipedia.

[glamcem]

Originally Posted by CSG Mike

I love wikipedia.

I do too

[bfrank1972]

Originally Posted by glamcem

yes Evo and STI has a slight disadvantage on drag coefficient figures (.27 vs .30X something) but that disadvantage becomes negligible especially when the speed increases ..see below formula:






I was referring to the highway pulls not the transient lag that is inherited in turbos, I should've said "better matched gears" because taller gears only have advantage for that specific power levels ..M3 with it's longer gears will almost always walk away from the SC'd FRS/BRZ with less than ~300whp


compared to other FI choices yes but compared to NA? well we know the answer

Hi, unless I'm misunderstanding your post, there are some things that might need clarification:

1) As speed increases, drag coefficient becomes exponentially more important, not less important.

2) We're making broad assumptions based on power/weight ratios, but ignoring engine flexibility/area under the torque curve/gearing when comparing 2 cars.

Assuming we have two cars, exact same shape power curves, exact same power to weight ratio, exact same drag coefficient, same drive layout, we can say the following:

- The heavier car will be at a disadvantage compared to the lighter car because the heavier car will have to overcome greater inertia, which at some power point will create traction issues. High powered heavy car can't put the power down.

- The heavier car will have an advantage at higher speeds because force required to overcome the inertia and the associated traction problems will become less of an issue, and drag will become more of an issue. Given equivalent drag coefficients, the heavier/higher powered car will pull away.

That said, the FR-S is ligther AND has a lower Cd than most cars with equivalent power to weight ratios. Where the Jackson SC (and all other gear/bet driven centrifugal compressors) fall down is the power curve. They build boost on a slightly exponential curve relative to engine speed. The power is all on the top end, unless you have some fancy variable ratio drive to spin up the compressor at lower RPM's.

This is why you see positive displacement supercharger kits making around 240-250rwhp easily matching & possibly outpacing centrifugal kits making 270-280rwhp. More area under the curve - especially important on street driven cars.