Llb per foot or bhp?

[manchestermatt1986]

I was going to put this under the 'Na performance mods for 1zz' thread but didnt want to clutter it up.

Basically, iv heard before that llb per square foot of torque is more important than bhp if your after speed, is this true? Or is my quote mixed up?

I understand that a car with less bhp but bein lighter can be faster. But I'm abit mixed up about the whole bhp/ torque

[leffex]

To much Topgear

Horsepower = higher max speed
Torque = fast acceleration

[VVT-i]

 m http://www.epi-eng.com/piston_engine_te ... torque.htm m

Happy reading lol.

[andywood]

>200lbft + >200bhp =   s:D s:D  

Simples


Andy.

[manchestermatt1986]

Wow, cheers for the link above. Out tonight but will defo read it properly tomorrow.

The reason I ask, I don't mind how fast my car wil go max speed. I rarely do topend speed. But I do like to have quick acceleration. And from looking at some of the modifications I'n the Na 1zz thread. Some cars have added bhp over time but 'lost' torque.

I'm guessing the setup I should aim for is all torque based??

[mrzwei]

Basically, thats the outcome of fitting a turbo, you get loads more torque throughout the rev range (more power too but often high in the rev range).So if you want acceleration then that would be a difficult option to beat in terms of cost.

On a normally aspirated engine, to get more torque is more complex, you're looking at modifying the engine in terms of camshaft profiles, possibly fuel injectors, exhaust system, possibly the ecu map etc, etc, in short, a potentially expensive, experimental, incremental  process.  (Easier to just get more power but usually everything shifts up the rev range so for good acceleration everything is happening closer to the red line)

Also for more acceleration you could start messing around with wheel sizes and tyre profiles at the back (dangerous with the roadster) and final drive and gear ratios ( expensive).

Turbos these days are relatively inexpensive and you don't need massive boost or loads of other engine mods to get a significant, safe, performance (acceleration) increase and there is a second hand market on here and lots of expertise.

Pretty brutal technology, but it's bolt on and it works. Just a thought   s:D s:D

[Anonymous]

not as cheap as a turbo but if you can get hold of the tte supercharger kit it will give what you are after custerd has one. its a nice kit and due to being run by the engine starts giving right at the begining

[manchestermatt1986]

Ill get in touch with custard and iv been looking at turbos over the last year or so but just cant bring myself to pay nearly half what i paid for the car but then a supercharger will be even more expensive.

At the moment i have the mr-s gearbox which iv been told is 'long-drive' so i dont know if thats better or worse. Iv got rid of the precats and got forced induction.

At home i have some crower cams (stage 1) waiting to go in but saving up for a power fc. No postive or negative comment ment here - looking at wabbitkillas details on the 'na 1zz' thread, he has done similar things to his engine and ended up with more bhp but LESS torque. so now im unsure what to do.

Lets just say i cant afford a turbo or supercharger, Are the cams and pfc going to be the right direction?

[aaronjb]

The MR-S gearbox is short, not long. Better for acceleration at the expense of higher RPM for any given speed.

[nathanMR2]

Ive done the whole N/A tuning thing and looking back you realise for the money that you spend on bits and remapping is very high in comparision to the actual output.

I dont regret the N/A tuning i did as it was fun to have that bit more power and learn more about the car. However once you fit a turbo or likewise you just realise how much more power your getting for the money. Its more expensive to do but power to £ is far far outwayed.

If you cant afford it you cant afford it but be warned once you start uping the power you are envitabley going to want more. N/A will give you little gains. Turbo will put a big grin on your face. So far im on a relatively low output compared to some but it so outways the N/A tuning i did that i get the feeling that i wish i hadnt spent all that money doing it and just saved up for the turbo to begin with

[mrzwei]

This is a massive generalisation, but if you want more power from an engine then everything tends to get bigger: High lift, longer duration cams, larger inlet valves, matched / enlarged / polished inlet manifold, bigger injectors, matched freeflow exhaust system, higher compression, remap to maximise all of that. Quite a science really and you would be advised to consult a tuner who can suggest a package that will work (or Wabbitkiller who has developed a package that works and I'm sure others have too).

Conversely, if you want more low down torque then you don't want to start messing too much with the size of everything. The stage 1 cams may well offer a good compromise here, sounds like a 'fast road' setup which will increase both power and torque without requiring silly revs to get there. I don't know the spec for the cams.

Other way to get better acceleration of course is a heavier right foot and drive to the red line   s:D s:D

[manchestermatt1986]

This is a massive generalisation, but if you want more power from an engine then everything tends to get bigger: High lift, longer duration cams, larger inlet valves, matched / enlarged / polished inlet manifold, bigger injectors, matched freeflow exhaust system, higher compression, remap to maximise all of that. Quite a science really and you would be advised to consult a tuner who can suggest a package that will work (or Wabbitkiller who has developed a package that works and I'm sure others have too).

Conversely, if you want more low down torque then you don't want to start messing too much with the size of everything. The stage 1 cams may well offer a good compromise here, sounds like a 'fast road' setup which will increase both power and torque without requiring silly revs to get there. I don't know the spec for the cams.

Other way to get better acceleration of course is a heavier right foot and drive to the red line   s:D s:D

Haha i do have a heavy foot when it comes to it. I just love the whole go kart experience of when i get on country roads but sometimes i feel between gears, i drop it too low and its screaming or i dont drop it enough and im bouncing in my seat going "COME ON!" haha. to be fair i dont drive silly often. Iv had the car nearly 4 years now and when i bought it i thought it was a little rocket, now i want more because i cant ever see me getting rid of the car. I just cant afford to buy a turbo really, i would do if i knew 100% someone would buy it nack after id had my use out of it but thats just a gamble, i know it likely to sell but £4000 plus extras is a big outlay on my wage   s:( s:(  

The MR-S gearbox is short, not long. Better for acceleration at the expense of higher RPM for any given speed.

oh cheers for that. I didnt know where they were different till someone said it as a passing comment at ding day.

[Anonymous]

some turbos have gone for less than 4k. keep your eye out you never know something might come up that will suit. but people are right na really is not cost effective to give you an idea my currently na is pushing 187 but the engine parts if you were to buy would set you back 6k then you need a standalone ecu to run it properly like i found out.

[manchestermatt1986]

kept lookign at sp turbo but just couldnt fund it.

People may knock me for this but i have toyed with the idea of getting the cams and power fc and then putting nitrous on it just for when i want a 'blast'.

Its only an option - im still thinking what to do. Plus im thinking of putting a lightened flywheel on with a new sports clutch, but i dont know if this will add any torue?

[markiii]

flywheel won;t add torque but it will feel faster as it will rev quicker

all round good mod

nitrous , check you can isure it first most companies wont touch it

[mrzwei]

I think you will find that a heavier flywheel will give more torque. As Mark says, the lighter flywheel will let you get to where the power is quicker but you will lose out on turning effort and have to use the gears nearer the red line.

[andywood]

kept lookign at sp turbo but just couldnt fund it.

Keep an eye on the 'private sales' section then, sometimes people trying to sell a car + high output sp-turbo package end up having to split in order to get things moving   s:wink: :wink: s:wink:  


Andy.

[manchestermatt1986]

I think you will find that a heavier flywheel will give more torque. As Mark says, the lighter flywheel will let you get to where the power is quicker but you will lose out on turning effort and have to use the gears nearer the red line.

Im a reading this right - a heavier flywheel will give more torque but a lighter one will rev up faster? so a lighter flywheel would lose torque and i would have to keep the revs up high? Can you buy heavier flywheels? i thought that to upgrade a flywheel you always went for lighter ones

As for the nitrous, im with adrian flux and luckily they are one of the companies that will insure it. Not asked how much yet as im in limbo and dont want to mention it unless im defiently getting it

[mrzwei]

Yes you are reading that right and you wont be able to buy a heavier flywheel (I don't think).
Once you get the flywheel turning (and relatively speaking that can take a bit of time) then the momentum is difficult to stop so with a torquey engine it doesn't matter so much what gear you are in because the momentum will keep things turning. When you lose the momentum then you need to work the gears to get the power. So what n/a tuning usually does is try to maximise power. The result of this is that everything shifts up the rev range so that it all happens at higher revs at the expense of low rev torque.
In the days before variable valve technology some tuned cars were almost undrivable at street level.

I think that your cams and the flywheel route will give a good compromise.

[markiii]

lightweight flywheel will make teh car feel fast, so is aleways a good one

the lower rotating mass will also more than make up for any lost torque

[manchestermatt1986]

light flywheels, mwr do one dont they. any other goods ones people can recommend, i wont be putting this in for a while as it isnt a necessaty to change my clutch yet

[markiii]

Rps lovely bit of kit ppe can supply

[ChrisGB]

No idea why anyone would think a light weight flywheel loses torque. Makes no difference to torque output whatsoever. What it does do is give the engine less mass to accelerate, so particularly in 1st and 2nd, you will feel the car picking up a little quicker. On the down side, driveability can suffer and engine braking effect is magnified when you come off the gas.

Chris

[mrzwei]

Can you give a source for that Chris? My source says something like the increased turning  effort provided by the heavier flywheel increases torque in the same way that say a long stroke engine would. One might be before the event but the other one is after it.

[ChrisGB]

Can you give a source for that Chris? My source says something like the increased turning  effort provided by the heavier flywheel increases torque in the same way that say a long stroke engine would. One might be before the event but the other one is after it.

The torque is a product of the force going down the con rod. The flywheel weight makes no difference to this, but it does allow the whole system (piston / crank / flywheel / car) to accelerate a little faster all the way through the rev range, as some of the weight of the system is removed. That weight of the flywheel has to be accelerated significantly in lower gears, as the engine speed rises more rapidly, so trimming flywheel weight is desirable. Because the engine braking effect is increased I wonder if this confuses some dynos on the run down? Saying that making the flywheel lighter reduces torque makes as much sense to me as saying making the car lighter reduces torque. Flywheel and car are locked together when the clutch is up. The only time torque output would be reduced is at launch where the greater energy stored in the heavier flywheel (built up before the car was moving) would be helping get the car off the line. As soon as that energy is used up, (pretty much as soon as the clutch is fully engaged), the engine with the lighter flywheel is pushing the car harder than the one with the heavy flywheel.

Really should get back to work now  s:oops: :oops: s:oops:  

Chris