Christian and Beccy

iTrader: (14)

I don't think I am the only one that is wanting to know this, so lets try and make this a sensible informative reference thread perhaps??

I am wondering the following :-

1. What is the relationship, if anything, between a cars BHP and its Terminal Speed on the 1/4 Mile?

2. Is the Terminal Speed affected by anything? (Gearing, Conditions, Weight and any other variable factors).

3. What is it that causes a car to have a lower Terminal Speed yet a faster ET than a similar car or vice-versa?

Can we try and keep this clean and non-bitchy!!

Jon ERST S2

the time is down to grip. The Terminal speed is down to power.

i.e imagine a powerful car spinning on the line not actually moving anywhere fora few seconds then it gets grip and can accelerate to the terminal speed, so even if it got grip sooner the terminal wouldn't go up as its still got the same distance to accerate in. You've just lost a few seconds on the clock cos your not really moving anywhere cos your spinning.

so a less powerful car may get better grip and accelerate away faster and get to the line quicker because it's not wasted time wheelspinning but it won't be going as fast when it crosses the line cos it's got less power, so it hasn't managed to reach said speed in the 1/4 of a mile.

Well thats how i understand it anyway... I'm sure someone else can word it better than me!

Tony Turbo

Basically, all the faster cars have a higher terminal speed, even if it is only 1 or 2 mph. Which must mean I am on for at least 160.3mph at Brunters

M Brian

lol@tony.

quick times can is also down to power/weight as its not until higher speed that ultimate power comes into it.
similar to what jon is saying but not more than actual grip.

you saw what happened when it was motorbike versus f1 car on 5th gear... from the start you could see the bike get away better. both probably had similar levels of grip in comparison. but once the interia was over came the formula 1 car reeled the bike in.

B19-TRB

I believe i had low terminals @ brunters for my power!

also noticed that on 1 of my slower times i had a terminal 4 -5 mph higher than any of the others!

Christian and Beccy

iTrader: (14)

This is where the confusion comes from. Lewis, what was your terminal??

So, would it be correct to say that ANY car with a Power-to-Weight figure of, lets say 300bhp per ton, would theoretically do the same terminal, regardless of whether it is FWD or RWD?

Jon ERST S2

in theory but aerodynamics will play a part. A bus with the same power to weight ratio wouldn't get as high a terminal than a rst.

Mike Rainbird

iTrader: (3)

1. What is the relationship, if anything, between a cars BHP and its Terminal Speed on the 1/4 Mile?
Zero, it is not about power, but POWER TO WEIGHT . Eg. You cannot compare two things of the same power, unless they are of the same weight.

2. Is the Terminal Speed affected by anything? (Gearing, Conditions, Weight and any other variable factors).
All of those plus power to the wheels, traction available and speed of gear change (and / or number of gear changes).

3. What is it that causes a car to have a lower Terminal Speed yet a faster ET than a similar car or vice-versa?
More grip than power / More power than grip.

B19-TRB

think the 14.1 i did had a terminal of 104 & @ point i had a terminal of 109

Mike Rainbird

iTrader: (3)

The difference in terminals in the same car is all down to launches - look at the differences in your first 60ft times. When you get a higher terminal but lower ET, this will be down to a poor launch...

K3V HA

1/4 mile times confuse me loads! LOL, i got 14.3 but a terminal speed of 98mph, think this means that i had a shit start

Benn 304R

once again Mr C, I told you you should of let me have a go

Jon ERST S2

My old car did 14.2 @ 112mph. So that indicates decent power but poor grip?

Christian and Beccy

iTrader: (14)

OK, so how it be said that your Terminal Speed relates directly to your BHP?

Example :-

2 cars. Both RWD Cossies.

Car 1 - 350bhp 2wd, 17" Wheels. Good Condition Road Tyres. Standard Gearbox. Experienced Driver (he can launch well)

Car 2 - 350bhp 2wd, 15" Wheels. Slick tyres (same Rolling Radius as the tyre on Car 1), Slightly shorter gearing. Driven by someone who launches in a cloud of smoke and wheelspin and snakes halfway down the track.

I know that to predict who would get the best ET would be difficult as that is largely down to the skill of the driver, the quality of the run etc etc.

But who would get the higher terminal and why?

Mike Rainbird

iTrader: (3)

John,
Yes it does... What would enable you to see this, would be if you got K3V HA to post up his timing slip and you did the same. You will see that he would have creamed you over the first 1/8th and you would then have done the same to him over the second 1/8th to then do a similar ET.

Christian and Beccy

iTrader: (14)

Also, what is a good 60ft time for a high BHP RST?

K3V HA

Ive got it somewhere mike, will try and put the times up, TBH, i think my 0-60ft time was shit!

Mike Rainbird

iTrader: (3)

Christian,
Wry you no wrisson?

Terminal speed is NOT related to bhp, terminal is related to POWER TO WEIGHT . i.e. a high terminal shows a good power to weight. If the ET is also impressive, it shows good traction as well . For a road car, anything over 110mph is VERY good power to weight, anything over 115mph is exceptionally good power, anything over 120mph is "oh my God" fast, anything over 125mph is "Oh shiiiiiiiiiiiiiiiiit" fast and anything over 130mph is other worldly!

In your example, the guy with the better launch will always get the faster ET, although he may get a "slightly" lower terminal on that run.

The terminals will only vary on the same car by 3-6mph providing that no changes are made to the car, even though the ETs can vary considerably due to poor launches (i.e. too much wheelspin). This is because the power to weight of the car remains a constant, but the traction is a balancing act....

I have every single one of my runs recorded and the difference in terminals is minimal, even though the ETs vary due to the launch (either bogging or wheelspinning). The only time the terminal varies wildly on the same car is when gears are missed or you do something to either radically improve traction or the power to weight (or both).

Christian and Beccy

iTrader: (14)

Mike I do listen, the point in my example was that the cars are the same Power-to-Weight.

I think you know what I am getting at, so I will cut to the chase.

Why is it that RS Turbo's seem to be judged on their 1/4 Mile Terminal Speeds? i.e. If a car, like mine, only manages 105mph Terminal, it is assumed that it does not have as much BHP as one that manages a Terminal of 110. I am trying to understand the relevance of the variable factors (Turbo characteristics, Tyre Size, Gearing etc etc)

Take Jon's for example. He has managed a Terminal of 112mph with, I would guess around 270bhp? My car is obviously quite powerful, lets say for arguments sake it is 250bhp, although I believe it is more than that. Why is my Terminal so much slower than Jons?

Jon ERST S2

My old car was 288bhp.

Maybe you got less power than you think

In all seriousness... I don't know!

Mike Rainbird

iTrader: (3)

Without having your FULL times to compare against John's (or anyone elses) you wouldn't be able to see where you are losing out , so it is pointless you looking at the ET and terminal in isolation . You need to be comparing your 60ft, 330ft, first 1/8th terminal, first 1/8th ET, 1/4 terminal and 1/4 ET with a car that does a "similar" terminal to what you want to achieve and then you can see where they are faster than you and where your improvements can be made (if possible) .

Also just to remove a specific factor, you need to let someone who is known to be exceptionally good at launching a FWD car have a go, just to make sure it isn't just YOU .

CliffRS4

iTrader: (1)

An interesting read, keep it coming

Christian and Beccy

iTrader: (14)

Thats a fair point about the power thing. But can my car really be less than 250bhp, considering the spec and its achievements? So, assuming that it is at least 250bhp, can that 38bhp really make 10mph difference on the Terminal? If thats the case, then I would be interested to see a list of each RST and its Highest Terminal.

On Sunday, I had problems with Actuator Pre-Load and Turbo Surge, which was only allowing me to run 22psi. I would normally be looking to run 26-28psi, could this have really made a significant difference to my Terminal Speed?

How about another comparison. I really aren't sure of exact details, but I thought Tims best terminal was 107mph? AFAIK, he was claiming around the same power as Jon, if not more. So, how does this work?

I am wondering how engine configuration affects Quarter Mile stats. Looking at it at its most extreme.......

Nissan 200SX. S13. 1.8 16v.

Car 1 - 350bhp. Fairly run of the mill car road car.

Car 2 - 600bhp. Massive GT Spec turbo laggy as hell (but great for BIG BHP numbers and Top Speed), not making decent boost until 5000rpm.

Who will have the best terminal?

timrud

Top stuff this thread!

I'm close to a 110mph terminal, few more tweeks on the car and hopefully I'll be there

Karl

Christian, Tims best terminal with 260bhp was 108mph.

When we changed to the T34 and 300bhp, the best was 109mph, but his qtr times were slower. The reason for this was because Tim had fitted ditchfinder 16's with a 45 series tyre to increase his top speed, but sadly made launching at the pod impossible!!

Olis running 320bhp at the pod managed a 114mph terminal.

Mike Rainbird

iTrader: (3)

Christian,
I thought you said you listened? The car with the highest power to weight ratio will always have the higher terminal speed, even if it has a slower terminal time...

Why are you obsessed with this? It isn't who has the highest speed across the line (which is only an indication of power to weight ratio), it is who crosses the line first, which is an idication of a better overall package (traction / power to weight / ease of launching / good gear change / no lag etc).

If you ever went up against Ollie and actually beat him over the line, but you got a 10mph slower terminal, you would still have beaten him and it would prove your package (for the drag strip) is better than his . You set a car up for what-ever discipline you want to do well in or you satisfy yourself with a compromise .

rs_si

I've attended 3 quater mile events in my car all with exactly the same spec. (257bhp + 338lb/ft)

1st was at brunters with performance ford = 14.6 @ 99 mph
2nd was at brunters with fast ford = 13.8 @ 107 mph
3rd was at TOTB3 = 14.2 @ 99mph

Everything was the same i.e. 17inch wheels with avon tyres (yoko for TOTB3) 1.5 bar of boost. The only difference between the three events was Brunters with fast ford I had about 20 runs whereas TOTB3 I had about 2 runs.

Stavros

Chris- Gawd knows why you keep asking as mike has said it 1000times already but the car with the most POWER to weight will have the highest terminal, providing he doesnt slowly wheelspin up the track.

Poor grip often wont affect terminal speeds as you dont really move forward much when spining so once you grip you still got just as much room to accelerate.

BETTER grip often gives you a very sligtly lower terminal speed tho, and im not sure why.

IMO 1/4mile terminal speeds are a better test of a cars ability than some gay RR/Dyno run...

Mike Rainbird

iTrader: (3)

Si,
The terminals will aslo be different due to the way they are measured. For FIA events the terminal speed is measured over an average of a distance (the last Xm of the quarter).

With the timing gear that is strapped to the car, it will give the speed of the car at the exact point it reaches 402m, due to it getting the speed / distance sampled several times a second from a satellite.

hooked_on_boost

Very interesting thread this nice one Mike R for the info in a format I can understand!!

I was confused by the times/breakdown on a Pod slip but I thought I was the only one who didnt understand and was worried about asking!

nice one!

p.

Hansenturbo

last year i did two runs 13.8@110mph and with wheelspin in 1 and 2 gear

Christian and Beccy

iTrader: (14)

Mike/Steve,

The reason I am so interested in this is simple......

In the past other people (Such as Dingy) have said 'Your car can't possibly be X BHP because your Terminal Speed is only Y and Oli's Terminal is Z

I conflict this by saying that I have taller gearing, no launch ability etc etc and am told that this makes no difference.

I'm sure others have wondered the same thing.

I TOTALLY understand the concept of Power-to-Weight, which is the reason for my line of questioning. This thread seems to have uncovered several RST's (which must all weigh a very similar amount) with similar claimed power figures, therefore similar Power-to-Weight but starkly different Terminal Speeds.

Matt

a long time ago now C but as you asked for 60ft times ....

Stavros

Chris- GEARING will have an effect, of course it does.

Grip doesnt that much tho.

Christian and Beccy

iTrader: (14)

Halleluyah!! Thats the answer I was looking for.

Final example!!

RS Turbo. 1600CVH. 300bhp. T34 Turbo. Same driver, same day.

Car 1 - 195/50/15, Standard Gear Ratio's, Standard Rev Limit (6250)

Car 2 - 205/40/17, Much taller Gear Ratio's, 7000rpm Rev Limit

Which would make the highest Terminal?? (Remember they both have the same BHP)

Christian and Beccy

iTrader: (14)

Mt 60ft times were nearer 2.3 on Sunday. Is this reasonable?

Mike Rainbird

iTrader: (3)

In my experience in my Sapphire, the gearing played very little in it. When I had the 3.36 gearing on, the quarters and terminals were almost identical, as despite the "slower" acceleration that this may give, I was able to go through the line with one less gear change that made up for it....

I would imagine that this works similarly to shorter gearing, the greater acceleration may be lost to some extent from the extra time required by the gear changes?

Christian and Beccy

iTrader: (14)

I can see the relevance of Gearing on the ET and can also see that there is a positive and a negative there, which could outweigh each other as Mike says.

I can't really understand how a car that had taller gearing would necessarily do the same speed over the same distance as one with shorter gearing.

Look at it as a race over a distance of 1 mile with the 2 RS Turbo's I mentioned above and tell me who would be going faster after that distance?

Karl

Mike I disagree with you about your power to weight theory affecting terminal speed.

Power to weight directly affects your time but has little effect on terminal speed. Terminal speed is primarily determined by power and drag coefficent.

For example a few years ago I ran a westfield with a 110bhp X-flow engine in. It ran a 14.0sec qtr, which is quick for the power but with a terminal of just 84mph. The same engine in a mk2 escort wieghing twice as much would give perhaps 16 - 17secs, but a similar 80mph terminal.


Ulitmately it makes obvious sense. The lighter the car for the same power, the quicker accelerating it will be. However as speed rises wind resistance becomes the dominant factor and this is primarily the power V aerodynamics.

Another good example is I have a couple of friends with mk1 Golk 16v's. Both run around 170bhp. One is a stripped out sprint car and weighs 700kg, the other a caged road car at around 900kg. Both achieve terminals around 95 -100 mph but the 700kg sprint car runs 13's as opposed to high 14's for the 900kg car.

Stavros

Karls got a good point there.

Weight affects you less and less the faster you go