Equal!!!!! LOLOL Coming home last night on a private motorway , i came up behind my mate in his very nice E36 Beemer 318 iS.... i slowed beside him, gave the wave and away we both wentfrom 65mph.... completely side by side upto just over 120!!! The good old deisel was still pulling when i decided enough and slowed down Now im impressed with the Bora doing that.... standard 110 TDi on 18's! My mate, on the other hand, wasnt impressed LOL. We then left the privately owned motorway and headed home at the national speed-limit Edited by: SiVWW
yeah, i drove a 318 is coupe once and it was, how to i put it, conservative on performance! 325, 328 and m3 are fairly quick though!!
BMW 318ti/318iS 140bhp 130 mph 9.9 secs to 60 -------------------- Volkswagen 1.9 TDi (110 bhp) 110bhp 120mph 10.9 secs to 60 the performance figures aren't that far off each other tbh, that bmw isn't exactly a quick car...and considering you raced from 60mph, the old diesel torque would have been doing it's job to make up for lack of bhp. not surprising you kept up really! Edited by: b'locks
Most 110 TDI engines put out more than quoted (around 115 - 130bhp). But it's the torque that matters. Standard figures are 173lb/ft @ 1900rpm, and if you started @ 65mph, then that's it's strong point - mid range.
yes, torque and power are positively related, but if he has 173lb/ft @ 1900rpm, then that doesnt relate to much power at 1900rpm. Relative to the bmw is does, which is probably why he could keep up, even though he has a deficit on peak power (as max torque is developed low down) he has the advantage with peak torque (albeit lower down in the rev range) relative to the bmw.
They're negatively related too you know... It's more accurate to say they are proportionally related. Irrelevant. Torque is the only thing that counts. HP is just calculation derived from measured torque at a particular RPM. HP is not a measurable quantity at all. Also remember, maximum in gear acceleration occurs at the peak torque point. The reason the TDI kept up was torque spread over a particular rev range, and appropriate gearing. It was probably close to its torque peak at 65mph too. Cheers, Drew.
?? yeah but my point is that 110bhp in a petrol car is not going to equate to the same amount of torque that you would get in a diesel car with the same bhp.
This is news to me, when does power decrease when torque increases? They are positively related, they follow the same direction when increased or decreased. I thought it was relevant as the BWM has a higher peak power reading, so the reason that the TDi could keep up is it's low down torque (which only relates to 110bhp peak power as its spread is developed low down (because as you correctly say that power is torque at a set RPM (the higher the RPM times the torque, the higher the power))) Isnt that right? Edited by: S1MMA
Bzzzt. Wrong. That is inversely proportional. Proportionally means they grow in the same direction (negatively or positively) related by some kind of factor. In this case it is hp = (torque x rpm) / 5252 ...and.... Power figures are irrelevant. Notice at 65 mph (in 5th gear?) the TDI is at its torque peak. This is where it is going to accelerate most strongly. Yet the calculation reveals that it is only generating about 68 bhp at this point. Yet it will accelerate faster here than when it is generating its full 110 bhp further up the rev range. A higher peak power reading means very little in practice. It simple indicates where the torque is within the rev range. You also need the torque curve and the gearing of the two cars to make a meaningful comparision. Yes, true. But your original post said that the TDIs torque 'made up for its lack of hp'. This is not accurate. You cannot actually compare HP figures across different engine types and hope to get a meaningful comparision. Things to remember...! 1. HP (an BHP for that matter) does not exist! 2. Torque is the ONLY thing that counts. Cheers, Drew. Edited by: drew
I studied that if something is positively related to something else, they follow each other (can be negative or positive change in their values), if something is negatively related then if one goes up, the other goes down. I know what you are saying, but I just studied it different at uni, i did a lot of stats (not engineering).
erm yes I understand the point you are making, but I know what I mean't in my statement...i think you're analyzing it too much and maybe being just SLIGHTLY pedantic
I have been thinking about what you have said, that max in gear acceleration occurs at the peak torque point. I understand that power is derived from torque x RPM (we can leave the divided by 5252 if we were to compare power figures calculated by torque x RPM, as its a singular constant in the equation). I always thought that the maximum in gear acceleration occured at the peak POWER point, not necessarily peak torque. I always thought of power as being the speed at which torque is applied to turning the wheels (simple way of looking at it). So, if a car has a flat torque curve (flat spread of peak torque), e.g. 200lb/ft from 1500rpm to 6000rpm, like an E36 BMW M3 supposedly has (it has a flat torque spread, not 200lb/ft of torque), then I thought that it will have the fastest in gear acceleration at the peak power reading, at 6000rpm in the above example. If a car has a torque curve like this: http://photo.starblvd.net/S1MMA/1-5-1-1071603480?m=0&pg=0&ro =4&co=0 then from what you have said through this post, is that the point which it has the fastest in gear acceleration (in any one gear) is at 1000rpm, not at 6000rpm? Is that correct? I thought it would be at 6000rpm, as power is calculated to be a higher figure there. Can you clear this up for me, as from what I have learnt in the past, what you have said doesn't make much sense to me? I am no Automotive engineer, or engine designer, but would like to know what is right and what isnt. Thx. Edited by: S1MMA
no i'm completely confused. My golf had 165bhp and 280llbft torque thats all i know and it was f***ing fast don't understand engine science over my head and i thought i was relatively clever oh well [:^(]
In simple terms, this the way I think of it:- Torque makes the car go. BHP keeps the car going. Diesel & petrol engines have different power characteristics. Diesel engines don't have ignition, so advancing the combustion at the top end of the rev range is difficult. This is why diesel engines don't rev as much as petrols. That and the gearing. Power is limited, but the engine is more efficient than a petrol, so it develops more torque sooner than a petrol engine. In-gear acceleration is all about torque around the low & mid rev range. In the real world, torque is the factor that makes a car feel quick. BHP sells cars! Edited by: Jon TDI
