lastphaseofthis

iTrader: (8)

^230RWHP 13b powered^

rx7racerca

iTrader: (1)

And yet somehow my respect is lower now.

NOS is a brand name.

rotarygod

iTrader: (1)

Since the original question is simply, "Is it Possible to for a 13b without turbo, supercharger or bridgeport to do 160mph??" I'm going to say yes, it's possible. This question did not state what the weight of the car was nor even what type of car it is in. It also doesn't mention drag of the car or how long it is expected to take to reach that speed. It also doesn't state at what rpm it wants to hit that speed. It should be "possible" with the right setup.

In 1978 Racing Beat hit 183 mph with a 1st gen RX-7 that had a naturally aspirated 13B bridgeport. The original question is aimed at going 23 mph less. Since the faster and faster you go the more and more power you need for each additional mph, 23 mph less is actually quite a bit in terms of horsepower. I don't see why it wouldn't be possible.

If the OP is trying to hit this in a street driven 2nd gen, since this is the 2nd gen forum, with nothing more than a streetport and some good tuning, I'd say that may be asking a bit much. A stock port engine in an S5 2nd gen can approach 145 mph but it is taking a while to do it. Another 15 mph is actually quite a lot in terms of power. I wouldn't say it's impossible, but I would say it will be a pretty tall challenge in a streetable car.

The other question is where is this attempt going to be made? If it's on the street, I want nothing to do with it.

Valkyrie

Weight is irrelevant at that speed. It could be the weight of a semi, as long as it has the same size and shape of an FC... Drag increases with the square of speed, not by the cube... But that means when you go from 130 (factory top speed of a stock NA) to 160 (top of factory speedometer), you need 50% more power, which means 242+ HP, which means you need a bridgeport, P-port, NOS, or a turbo.

That, or you need to cut drag by 50%...which isn't going to happen.

rx7racerca

iTrader: (1)

Drag itself varies with the square of velocity, but power needed to overcome drag varies with the cube of velocity:

Pd=1/2(pv^3)*A*Cd
http://en.wikipedia.org/wiki/Drag_(physics) - section 2.1 I know it's wikipedia, perhaps a little less reliable than Britannica or an engineering text book, but it is accessible online readily.

So I'm pretty sure my estimate based on the % increase in velocity is fairly accurate in predicting ~285bhp needed, or 240+rwhp. Which isn't going to happen with bolt on mods (exhaust, intake). It pretty much calls for turbo/supercharging, really.

On the other hand, the OP really just said he dreamed of seeing the speedo hit its end at 160 - which he could readily achieve by putting on undersized tires and running it flat out. No mods required, just some small diameter tires/rims - something with an overall diameter of ~20" - maybe a Hoosier A6/R6 225/45-13 Not a lot of options in low profile, small rim tires.

Either way, like Rotarygod said, I don't really want to be an enabler for what seems like a dumb idea. But at least faking the speedo with small tires wouldn't push the car quite so far beyond reasonable speeds, since I think it unlikely this apparently low-budget effort (based on the assumptions of no brideport/super/turbocharging) is likely to be taking place on a track, or with a cage or other safety equipment)

scathcart

Underbody turbulence and ground shear cause a good majority of aerodynamic drag; most any reasonable attempt to limit it will always result in a decrease in total drag, and an increase in total vehicle download. This has been common knowledge since the engineers at bonneville realized this nearly 60 years ago. There most certainly are free lunches, take a look at all the ground effect chassis' of the late 70's and early 80's; insane amounts of downforce created from a very marginal increase in drag.

rotarygod

iTrader: (1)

The aerodynamics of a good Bonneville car is to get them as low as possible and to have as much air as possible directed around the car, meaning a front air dam that is just about scraping the salt as it goes by. These cars still have very smooth underbody trays. They also run narrow tires.

rx7freak13v

you guys make this sound impossible.i have a 88 gxl with stripped interior from the seats back.tockico struts and 2inch drop all around a front strut tower bar,long tube header with 2 1/2 inch pipe with 2 cats and a GP sports muffler,a K & N filter and a stage 3 f1 racing clutch and poly motor and trans mounts.stock ports about 140k miles and i have acheived 157 by the cops radar gun when my rear wheels were skipping on the pavement and i had to slow down (that was before the 2inch drop) oh yea i also have a msd 6a coil feeding the leadings.i did that on the highway.the cop was a budy of mine and we wanted to see if i could do it.btw,my s4's speedo rapps out at 150mph.also i've guted useless things as ac,power steering and a bunch of other non useful stuff.if i can find the ticket i'll post it up.btw,my tires are not rated for that kind of speed and i was retared for attempting but im 21 and i was 16 then so 5 yrs ago.it's stupid scary when you can feel the rear wheels skipping.it's retared and should not be attempted without proper tires and saftey.im building my fc for autocross and am doing a holly conversion in october and planning to port in the spring,planing a wild street port.i would go bridge but still plan to drive....daily

rx7freak13v

btw,not a real ticket but explaining the yr make and model with date and speed. forgot to explain that.and meant to type 147mph not 157mph my bad.i didn't even realize i typed 157 until after i posted and re read the post and i seen i forgot to explain a few things.but if a stock port s4 can almost wrap out to 150mph why can't a stock port s5 wrap out to 160mph?i don't get it?yea it sure takes some time and alot of roud but possible.i live in north central florida so long straight flat highways........

rx7racerca

iTrader: (1)

I've made it sound impossible, because I believe it is, without using boost or Pport or other internal mods, which the OP said no to. An S5 made all of 14 more horsepower than the S4, and in contemporary magazine testing, that got it a whole 2 mph faster top end - at 130 mph. Stripping out weight is of little consequence at those speeds, other than in how long it takes to accelerate to top speed on a flat road, it's all aero, and power. Lowering the car a lot, building a full undertray, and adding a front splitter could all help, but aren't going to make a silk purse out of the NA sow's ear. Even a stock S5 (200hp) was only good for 140mph back in the day, and that's with significantly more torque and power than even a significantly modded S5 na will put down.

Did your cop friend show you the reading on the gun? Because it does occur to me that it's really nuts for a cop to be letting a 16 year old make top speed runs on a highway, in an old car without tires rated for the speed. Maybe he just told you a little white lie to make you happy and call it done? Unless there was a strong tailwind, or downhill involved, I'm hard put to see it.

PvillKnight7

iTrader: (16)

impossible in a stock 2nd gen

junito1

Its possible all day.

PvillKnight7

iTrader: (16)

That day must be Nonday because it's not going to happen.

You best educate yourselves fools:
http://www.getfaster.com/Techtips/Physics6.html

jgrewe

iTrader: (1)

I lost track of everybody's conditions of what will work and what won't to reach 160mph but here is my input.

Our E Production spec cars have to run a street port, weigh 2300lbs, 2" wider fenders each side. The dataq says they hit an aero wall about 156mph at Daytona. The gearing is not quite right but the right gears aren't available with our combo, probably about 700rpm away from peak hp at that speed. A stock body with all the tricks to help aero might get us there with the power and gearing we have.

160mph possible, not probable.

rx7freak13v

i guess u could be right on that one.i didn't see the actual reading.however,my roomate drives a 95 neon with some work done to it,it's aerodynamicly declined almost.he has a laptop with a rather expensive gps set up that reads speed mph.i wsa tailing him when the gps reached 131mph (shows on the gps highest top speed) and thats where his little neon reached its limits.i finaly decided to pass him when he stopped accelerating and left him sitting there with a nice view of my s5 tails as i dissapeared into the distance.i just wanted to show him that his lil 2.0 could not hang with my 13b.we stopped in at the pilot station when he showed me the results.if he topped at 131 by the gps and i pulled like crazy once i actualy planted the pedal (lets face it,u don't need wot to tail a neon) then that means i deffinitly reached much higher than 131 cause if i was only a few mph faster then i would have pulled slowly and i deffinitly walked on him.i didn't get a speed reading on my gauge which sucks,about the time i planted the pedal and blew by him my speed cable snapped (again,i got it from advance auto and they roll it up into a small box,im now on speed cable 7.at least they keep replacing them for free lol).i live in north central florida (ocala area) so our roads are mostly flat or at least seem that way,i guess there could have been a little downhill but nothing much if so.i dunno.not building for speed though,im building for autocross,but for now it's also my DD.planning a holly conversion in the fall and a large street port next spring.

Silvertear

iTrader: (3)

If you want to go in a straight line, why are you in a 7?

The whole point of buying an rx7 is to kick it sideways here and there. Just take it out to some winding roads and feel the car. You can get way more excitement out of 30-40 mph on a road with lots of hairpin turns than you would get crawling your way to 160.