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-   -   Whats the right amount of horsepower? (https://www.rx7club.com/v-8-powered-rx-7s-299/whats-right-amount-horsepower-1089767/)

gabescanlon 09-18-15 11:55 AM

Whats the right amount of horsepower?
 
Yeah yeah I know, you can never have enough. Well, Im wondering what a good amount of horsepower would be for my ls1 swap. I was thinking 400, but then started to think I might want 500..

Anyone, speaking from experience, know if 400 hp is enough in an rx7? or if 500 hp is too much for the street in an rx7? Whats the cap for the street before it becomes impractical as a weekend/daily?
I have a 93 fd Btw.

gabescanlon 09-18-15 11:56 AM

Will be a street car only, wont be tracking it

Littleguy 09-18-15 06:03 PM

I feel like between 450-500whp is perfect for Houston.

gabescanlon 09-18-15 06:28 PM

So the car still runs pleasantly at 450-500 horsepower?

Littleguy 09-19-15 10:28 AM


Originally Posted by gabescanlon (Post 11969744)
So the car still runs pleasantly at 450-500 horsepower?

With Toyo R888's it is great as long as it isn't cold or raining.

stickmantijuana 09-19-15 10:53 AM

400whp is plenty fast on most tracks on performance street tires. you can never have enough on long straights. in other words, if your rush comes from trying to bury speedo needle as fast as you can on freeways, you will never ever have enough whp. do keep in mind though, at over 400-500whp, you can literally kill yourself and other people quite easily. so respect the power and be safe. at double or triple the power, it can only take a split second of misjudged WOT to ram into other cars, trees, and people. I only say that because it sounds like it's your first time going into 400-500whp range. it's quite something else.

Natey 09-19-15 11:48 AM

Most race cars (touring, ALMS, etc) have about 400HP. Any more and it becomes harder to drive fast.
Spinning tires don't make you go faster. heh, They just make it scarier.

On the other hand, I agree with stickman. If you wanna smoke people at stop lights and "light 'em up" then by all means, put a 500R in there, turn up the boost, and don't forget the fuel rail. :icon_tup:

rafgonz 09-21-15 05:55 AM

Are we talking HP at the wheels or at the crank? My old FD had 330hp to the wheels and it was pretty fun and enjoyable to drive. Most days it felt like it was more than enough for a daily driver. I agree with stickman and Natey. Personally I found out that it was better for me to invest time at the track learning to drive faster than to add HP. The car was much easier/enjoyable to drive when I was not trying to fight the steering wheel etc. Keep in mind that your tire will also make a big difference as to how the car behaves. Sometimes its best to work your way up and see where you are comfortable before you find yourself in serious trouble.

LargeOrangeFont 09-29-15 03:07 PM

400-450 WHP will be a VERY fast car. There will be few cars on the road that can hang with you.

My FC has 400 WHP and is a bit lighter at 2600 lbs. At the track the car pulls on or hangs with nearly everything on the straights.. New Vipers, 458 Ferraris, Turbo Porsches, C6 Z06s.

In a FD street car 450 will get the job done but you will need big tire's to really use the power. As you get past 525 or so WHP it will become unusable. The sweet spot is between 400-500 WHP depending on your skill and setup.

BLUE TII 09-29-15 04:01 PM

I do know 420/420 rwhp/rwhtq in a turbo rotary isn't enough in a 2,500lb FC for me.

However, you only need enough HP that you are never at full throttle.

I never once spun the tires in 5th gear even at full throttle.

For an LS swap I would aim for 1,000hp and turn the boost down for reliability if you never find yourself using full throttle.

That is my plan if I LS the FD. I mean, a twin turbo kit is the same price as a pair of LS swap headers- so why not?

Littleguy 09-29-15 06:55 PM


Originally Posted by LargeOrangeFont (Post 11973899)
400-450 WHP will be a VERY fast car. There will be few cars on the road that can hang with you.

My FC has 400 WHP and is a bit lighter at 2600 lbs. At the track the car pulls on or hangs with nearly everything on the straights.. New Vipers, 458 Ferraris, Turbo Porsches, C6 Z06s.

In a FD street car 450 will get the job done but you will need big tire's to really use the power. As you get past 525 or so WHP it will become unusable. The sweet spot is between 400-500 WHP depending on your skill and setup.

Agreed with everything.

LargeOrangeFont 09-29-15 09:26 PM


Originally Posted by BLUE TII (Post 11973917)
I do know 420/420 rwhp/rwhtq in a turbo rotary isn't enough in a 2,500lb FC for me.

However, you only need enough HP that you are never at full throttle.

I never once spun the tires in 5th gear even at full throttle.

For an LS swap I would aim for 1,000hp and turn the boost down for reliability if you never find yourself using full throttle.

That is my plan if I LS the FD. I mean, a twin turbo kit is the same price as a pair of LS swap headers- so why not?

FWIW I'll be upping the power to about 450 WHP and calling it good. The car lays over in 5th, but part of that is the tallish 5th gear in the T56 I have in the car. I can't fix that without swapping the trans.

Monsterbox 09-30-15 11:25 AM

This 20b has made over 740rwhp on 22psi, with plenty of room to go. I built the car for big HP and hardcore interstate pulls.

Truth is, after a year of building it and dreaming of these huge #'s, lowest boost possible @ 10psi 500rwhp scares the living shit out of me in 1st and 2nd gear!

I've swapped out the wastegate spring to run a max of 12-13psi, and have never even tried more power than this besides the dyno!

550-600rwhp in an FD is just flat-out insanity. Anymore and you're a nutjob. This car barely stays planted in 3rd gear at WOT at 13psi. Its stupid, overkill. I feel ridiculous for choosing an 80mm turbo and shooting for 800hp.

This isn't a supra or a GTR, its a lightweight toy machine.

mattster03 09-30-15 05:48 PM


Originally Posted by LargeOrangeFont (Post 11973899)
400-450 WHP will be a VERY fast car. There will be few cars on the road that can hang with you.

My FC has 400 WHP and is a bit lighter at 2600 lbs. At the track the car pulls on or hangs with nearly everything on the straights.. New Vipers, 458 Ferraris, Turbo Porsches, C6 Z06s.

In a FD street car 450 will get the job done but you will need big tire's to really use the power. As you get past 525 or so WHP it will become unusable. The sweet spot is between 400-500 WHP depending on your skill and setup.

Stamped & approved.

Rbkouki 09-30-15 10:47 PM

Mosnterbox said it best, numbers arent the same for thee things as they are with other cars. At 468 WHP my last LS1 fd was fast enough to hurt plenty of 900 hp club feelings at the track.

People get caught up in the hp numbers and disregard all the other variables that should be considered.

ZDan 10-08-15 07:15 AM

For my S2000, ~150hp (about what it makes out of VTEC) is sufficient for 99% of my street driving.
For the FD, ~525hp was only enough for ~185 in the standing mile, so obviously it needs more. Hence new 6.9 LS3 now installed, bout to get dyno tuned :D

Timeless 10-08-15 07:28 AM

Mine currently has 305whp and will be mainly road course/nice weather used. It is power to weight faster than my previous higher HP cars (2005 E55 AMG/2011 Mustang GT) and feels it especially since it does not have any nanny assistance.

My plan is to get used to what I have and then maybe add longtubes and a more aggressive cam to get it to around 400whp and call it a day after that.

I can tell you that tires make a huge difference in the usability of the power. When I got the car it had 255/40/17 tires on rear that were run flat and you could get sideways very quickly at even higher speeds/gears. Now has 275/40/17 Nittos and the grip is so much better and more friendly.

tbkonwso 10-08-15 06:36 PM

400-450 is more than enough on a V8 FD

frijolee 10-12-15 08:12 PM

Best guess my FC is somewhere a little north of 550 rwhp (429 LS2 stroker with a great deal of breathing work). After I lost it lighting up third--on 295 summer tires and 3.55 gears mind you--I can say that's a bit too much power for the street. Worst part... I have a racelogic box setting on the shelf I hadn't gotten installed.

Damage wasn't bad, but it was a bit odd to feel like I actually found the limit of fun street HP.

Exidous 10-14-15 04:28 AM

It's funny, at 420whp and 375rwtq I could easily walk c6 Zo6's and lightly modded gt500's. The combo wasn't right though. Felt like a dog down low. Completely redid the top end. Gained at least 30whp and 40rwtq and feels awesome down low. I will tell you that about 450rwhp is about the happy number. Sure there will always be fast cars on the long interstate but on the track it's just right with some 180 tread wear summer tires. Or r888's if you really want to stick.

My vote is for 400whp with 220+ tread wear tires and 450whp for softer tires. I can tell you that 300 tread wear 285 wide tires is freaking useless with 375rwtq in 1,2 and 3rd. (4.10 rear)

BLUE TII 10-14-15 11:51 AM

300 tread wear 285 wide tires is freaking useless

Exidous 10-15-15 04:28 AM

Unless you are driving a long way and don't have a big tire budget. I'll certainly never buy them again but as I said in my last line. They are useless indeed unless it's your daily driver.

BLUE TII 10-15-15 12:22 PM

Yeah, it just seems to me the primary market for high treadwear wide tires is people who buy an expensive performance car and then wear the stock high performance tires out in no time.

They cheap out and get low performance tires because they are cheaper and will last longer and they don't drive their cars hard enough to notice a difference or care.

Really, they would be better off with the non performance version of their car that came with narrow wheels and tires or at least those wheels/tires.

A 285 sucks in the rain and snow whether it is an all season or not- would be better off with a 245.

That is all I mean.
A performance tire size in a non performance compound just seems like a poor compromise to me. Even for just looks, anyone who knows performance looks at a car's tires first when judging a car's performance potential.

Littleguy 10-15-15 05:58 PM

Absolutely agreed. In fact, when someone is talking trash I will just look at their tires and be able to see if they are serious or not. Above 100 tread wear and you won't get my respect, lol.

ZDan 10-15-15 07:42 PM

Treadwear numbers are not directly correlated with grip. Particularly grip on the street. At 50F in normal street driving conditions, good high treadwear all-seasons can have significantly more grip than Max or Extreme perf summer tires.

Best tires for grip depends on usage conditions. And even for dry track usage you shouldn't assume lower-treadwear # => more grip. There are tires that have poor grip and wear out quickly.

BLUE TII 10-15-15 09:06 PM


ZDan

Treadwear numbers are not directly correlated with grip. Particularly grip on the street. At 50F in normal street driving conditions, good high treadwear all-seasons can have significantly more grip than Max or Extreme perf summer tires.

Best tires for grip depends on usage conditions. And even for dry track usage you shouldn't assume lower-treadwear # => more grip. There are tires that have poor grip and wear out quickly.


In normal steet driving conditions you don't need grip... Yes, if you need to emergency stop when your tires are cold the distance will be longer, but in my normal driving there is someone behind me in an SUV that keeps me from ever using maximum braking.

If... you were alone... at night... 1 mile from your house...and a person jumped out in front of you... you might stop shorter and not hit them on all-seasons.

You probably just should have steered around them instead of hitting the brakes.

Push the Max performance street tires or DOT Rs a bit and they warm up and have much more grip.

You should say the high treadwear all-seasons are "more predictable" since they always have the same mediocre level of grip.

But 50 deg F?
No, its more like 35-40 deg F pavement temps (you usually notice it in the mornings) that max performance summer or DOT R tires won't heat up in normal sedate driving.

There are a couple tires that are terrible before they are warmed up even in temps as high as 50 deg F as you say. You can usually tell those because people in really hot climates love to race on them.

Our whole winter season of auto-x is 45-55 deg F and the only thing faster than max performance summer tires is full race tires. Even if it rains torrents no one wants all-seasons. Its full tread performance tires or REALLY SOFT rain race tires (that last minutes if it dries out).

I maintain my viewpoint that all-seasons in wide performance sizes are for basic people who bought a performance car/package for image and then were too cheap to pay for the actual performance.

BLUE TII 10-15-15 09:07 PM

And I think this is the PERFECT thread to be having this tire conversation...

ZDan 10-16-15 07:00 AM


Originally Posted by BLUE TII (Post 11980339)
In normal steet driving conditions you don't need grip...

You *MIGHT* need it suddenly and unexpectedly.


Yes, if you need to emergency stop when your tires are cold the distance will be longer, but in my normal driving there is someone behind me in an SUV that keeps me from ever using maximum braking.
100% of the time? You want maximum grip for real-world conditions on the street for that fraction of a fraction of a percent when you really do need it!


If... you were alone... at night... 1 mile from your house...and a person jumped out in front of you... you might stop shorter and not hit them on all-seasons.
This brings up a broader point I'd like to make: you cannot broadly categorize tires in terms of grip based on whether they are summer tires or all-seasons. There are all-season tires that are pretty well trackworthy (for a few laps anyway), there are some that have fantastic grip in warmer weather but suck in colder weather, and there are all-seasons that suck in all conditions.

Likewise there are wide variations in summer tire performance.


Push the Max performance street tires or DOT Rs a bit and they warm up and have much more grip.
Problem is, in the real world on the street, they're going to spend 99.9% of their time much cooler than their optimal temps. Even more true if they are wide tires on a relatively light car. My FD on 245/275 Michelin Pilot Super Sports has less grip on the street at 50F than our Mazda3 on General GMAx AS-03s. But of course the PSSs have WAY more grip at the track.


You should say the high treadwear all-seasons are "more predictable" since they always have the same mediocre level of grip.
AGain, you can't broadly say this about all-seasons. There are some that have barely less grip than Max Performance tires on the street (Michelin PS A/S 3). There are some that are skewed more to colder weather and snow. There are some that have reasonably stiff responsive sidewalls and plenty that don't. And there are some that just flat suck in all conditions (Bridgestone RE92, which probably prevented us from buying a new Mazda3 a couple of years back).


But 50 deg F?
No, its more like 35-40 deg F pavement temps (you usually notice it in the mornings) that max performance summer or DOT R tires won't heat up in normal sedate driving.
I've noticed it with the PSSs even after 15 minutes at 70-75mph. Very surprised at the very low cool-weather grip of those tires, IMO their not as good as the RS3-V2s on my S2000. Again, exacerbated by being sorta wide tires on a sorta (relative to modern pigs) light car vs. narrower 205/225 tires on the S2k.


Our whole winter season of auto-x is 45-55 deg F and the only thing faster than max performance summer tires is full race tires. Even if it rains torrents no one wants all-seasons. Its full tread performance tires or REALLY SOFT rain race tires (that last minutes if it dries out).
I would never suggest any all-seasons for autoX, even in the wet, that wasn't my point.


I maintain my viewpoint that all-seasons in wide performance sizes are for basic people who bought a performance car/package for image and then were too cheap to pay for the actual performance.
Can't broadly categorize either tires or the people who buy them!
If I'm getting tires for real-world street driving (i.e., not autoX, not racing, not canyon-carving) throughout the colder months (not snow/ice mind you, but say 35-50F and sometimes wet), I would definitely pick a top UHP all-season over any Max Perf summer tire.

Also reject the idea that cheap tires inherently have poor grip and that expensive tires are "better". There are GREAT tires available for reasonable bucks, and plenty of expensive tires that suck!

You just can't make any broad characterizations on tires.
Too many people think they can just buy by the brand and be OK, but no, most major brands make good tires and suck tires in all categories.
Likewise, you can't assume that a specific Max Performance summer has more grip (even in dry warm conditions) than a specific UHP All-Season, or that lower treadwear rating = more grip.
Nor can you assume that an "all-season" tire will have good grip in cool or cool/wet conditions, there are plenty that don't!

It's not enough to go by treadwear numbers and summer vs. all-season. Have to research the performance of the specific tire make/model to ensure your getting the best for your usage conditions.

wa11yba11s 10-16-15 10:01 AM

I think the HP number not only depends on the tire size, but also the gear ratio of your rear. If you have one of those lower geared diffs you might not be able to use 500HP.

gnx7 10-16-15 03:53 PM

I think 1000rwhp+ is a bit much on the street :)

In all honesty more than 550rwhp is hard to put down on the street unless you have an R-compound tire out back with 100 tread wear or less. A 275/35/18 can put down 595rwhp (440ci LSx) with 3.55's no problem.... if you want to overwhelm the tires you certainly can.

A 335 R compound out back really allows you to use HP. It's stupid to try to run a ton of HP with tires that aren't the best.

Littleguy 10-16-15 05:51 PM


Originally Posted by ZDan (Post 11980309)
There are tires that have poor grip and wear out quickly.

Good point! lol.

Nick Ritter 01-04-16 01:44 AM

288whp through t56 bone stock 6.0l through 4.10 gears very fun street car kinda quick compared to what you see on the street 2700lbs

BLUE TII 01-04-16 02:41 AM


gnx7

I think 1000rwhp+ is a bit much on the street


Where else can you use that much power but the freeway?

Its not really even going to help on the 1/4 mile- chassis set-up will get your times lower easier.

Freeskier7791 01-05-16 10:34 AM

what do you guys think about V8 swapped FB? 400whp?

XLR8 02-23-16 03:02 AM

I think it comes down to the purpose of the car. For me, I wanted 500-550whp as I felt that it was the limit of what was useable on the street. It's fun, and keeps me smiling all day. I break my 285's loose with half throttle in 4th if I give it the beans. But for a 30 series, they hold quite well with the Fordtrac 3.55's out back.

LargeOrangeFont 02-23-16 08:06 PM


Originally Posted by XLR8 (Post 12030841)
I think it comes down to the purpose of the car. For me, I wanted 500-550whp as I felt that it was the limit of what was useable on the street. It's fun, and keeps me smiling all day. I break my 285's loose with half throttle in 4th if I give it the beans. But for a 30 series, they hold quite well with the Fordtrac 3.55's out back.

What tires are you running?

Mr3plus1 02-23-16 08:15 PM

Depends on suspension/tire combo. I agree with most everyone saying 400-450. When I had mine I was running 335's in the back and they were r888s. While it definitely could have handled a lot more than the 400hp I threw at them I was still faster than 99% of the cars that I came across just driving around.

LargeOrangeFont 02-23-16 08:48 PM


Originally Posted by Mr3plus1 (Post 12031216)
Depends on suspension/tire combo. I agree with most everyone saying 400-450. When I had mine I was running 335's in the back and they were r888s. While it definitely could have handled a lot more than the 400hp I threw at them I was still faster than 99% of the cars that I came across just driving around.

R888s, NT01s, RC-1s or drag radials are almost a necessity with these cars over 400 WHP

The problem is getting and keeping heat in the 100 treadwear tires so they can really work well.

Ruler_Mark 02-25-16 03:25 PM

All the horsepowers

BLUE TII 02-25-16 05:24 PM


Ruler_Mark

All the horsepowers


Exactly!

Because there is always going to be someone faster than you, but maybe with enough HP you can beat them?

LargeOrangeFont 02-25-16 05:48 PM


Originally Posted by BLUE TII (Post 12032046)


Because there is always going to be someone faster than you, but maybe with enough tire you can beat them?

Fixed.

Littleguy 02-25-16 05:52 PM

Hahahaha

BLUE TII 02-25-16 06:56 PM

You just start from a higher roll on speed.

"Nah man, I spin anything under 160mph- lets roll on from 165mph."

From and actual imaginary conversation I just had.

Sai-Omega 02-25-16 08:19 PM

Reading through this makes me glad that my motor is putting out 527 at the crank.

The car ought to be a blast when I get finished.

ZoomZoom 02-26-16 11:40 AM

My LS3 FD put down 440/440 at the wheels and only drag radials could put the power down. One thing you need to consider is your rear end gear. The LS swap is already going to have a ton of torque off idle unlike you ever experienced with the rotary. This will equate to traction issues given the rear end and rear end gear you will be running.
If you are sticking with a stock FD rear you will likely be running a 4.10 or a 3.90 from an Automatic FD.
If that is the case expect plenty of wheel spin in 1&2 gears. If you are moving to a Ford 8.8 and a 3:55 gear it's going to be easier to put 400/400 down.

XLR8 02-26-16 07:53 PM


Originally Posted by LargeOrangeFont (Post 12031212)
What tires are you running?

Hankook EVO12's. They are pretty old, as I have put about 3k miles on my car in the last 5 years...lol. I got them as a quick solution. They definitely don't do bad though. On warm days, they hold pretty well. I definitely see a drag radial in my future though. A 15x10 Meister would look nitto too. ;)

runyun 03-17-16 09:21 AM

472 whp / 455 tq here.. I think its a bit much.
(was 345 rwhp previously - and that wasn't enough)

If I had to do it again, I'd go with what the majority said here - around 425 whp


note: I'm on stock rear end. 8.8 with 3.55 on the way, will update

tbkonwso 03-21-16 12:45 PM

i daily drive my fd with 2-3 track days in a year, car only makes 380 with a cam. im aiming for 430-440 hopefuly after more mods. i think that a 450hp with semi r compound tires like nt01 or r888 would be the perfect fun street car.


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