madmog
Club Retro Rides Member
Posts: 1,160
Club RR Member Number: 46
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Power to weight or size ratiomadmog
@madmog
Club Retro Rides Member 46
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Apr 11, 2007 20:44:06 GMT
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Is there a rule of thumb regarding how much power can be added to a car of a given size while still being reasonably practical? For example I'm sure there are a few small block Chevy v8 powered Fiat 500s out there but I wouldn't think they were very nice to drive around town or even on the motorway for long periods.
Or to ask a slightly different question, is there a point at which the increased power is of little use? E.g. Something small and light like an A40 with 200bhp might be awesome but 300bhp might be slower because of traction problems, lack of balance if a heavier engine fitted, or just be prone to flipping 180 degrees before the driver can react?
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Apr 11, 2007 21:06:06 GMT
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Ponder this myself, I never fancied a propper yank V8 in my Capri/Sierra projects, pehaps in a Granada, didn't think it would work too well! Been watching a debate unfold over at the MR2 club, standardish mk1 mr2 modded from 120 bhp to 170ish, or a mk2 turno installed mk1 weighing in upto 100kg's more but boastin 280bhp easily...   But the weight is mid mounted does that make it better/worse some say sure footed, others disagree and say its not as nimble. i know what i'd rather have given the choice i think. its scentific but i think you have gotta suck it n see in the real world |
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 it doesn't matter if it's a Morris Marina or a Toyota Celica - it's what you do with it that counts  |
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Hirst
Posted a lot
This avatar is inaccurate, I've never shaved that closely
Posts: 3,930
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Apr 11, 2007 21:39:06 GMT
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Wheelbase and wheel/tyre sizes are very important too. The problem is you can only do so much, especially with a smaller car.
Oh, and the chassis itself might not be up to the higher power!
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Apr 11, 2007 21:55:02 GMT
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a lot of mates run 400bhp mk1 escorts (about 900kg most of em come out at) with cossie motors, concensus is, they are a bit iffy in the rain, but the 170mph top speed makes it worth it.  |
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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Apr 11, 2007 22:24:21 GMT
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Good question....probably a million answers though. Two big factors would be what you want the car for, and how much the rest of the car has evolved around the power available. My Celica should be around 220hp/tonne (4.75kg/hp) which I think is a good place to start....... Just can't help thinking that stupid amounts of power would be fun if I could find a pointless outlet for it ...er like this - Burnout comp'Found this link listing loads of power/weight ratios. My 4.75kg/hp puts me up with WRX/Evo crowd OK I knows it's from Gran Turismo 4, but they take this stuff pretty seriously, so probably quite accurate info. |
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Last Edit: Apr 11, 2007 22:58:46 GMT by celicaV8
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topi
Posted a lot
It's a race car officer, I swear!
Posts: 1,039
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Apr 11, 2007 22:33:14 GMT
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I want to aim for 200bhp in my C20XE Opel Kadett (800kg ish?). Will be standard engine on R1 carbs to start with, but eventually I wan't to build something a bit beefier to hit the magic 200bhp. I think it'll be a good *usable* amount for the car.
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Apr 11, 2007 22:55:35 GMT
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Suspension setup is crucial. My mini will torque steer like its on rails (wavy ones) because the camber/caster/toe/height is not set. Also the scrub radius is large and the steering is heavy. All these can be largly overcome with the right setup, lower off-set wheels, metro hubs and powersteering, then the 180hp goes in a straight line !!
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my cortina will work out at about 200bhp per ton and thats a sensible amount to start with i reckon, enough for fun and some performance but not enough to make it an animal.
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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madmog
Club Retro Rides Member
Posts: 1,160
Club RR Member Number: 46
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Power to weight or size ratiomadmog
@madmog
Club Retro Rides Member 46
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What got me wondering was a posting here www.16vminiclub.com/forums/viewtopic.php?t=8844While the difference in timing might just be a case of learning how to deal with the characteristics, perhaps there's a point where the effort of controlling the power and the limitations of the chassis are more of a handicap than a gain.... It would be interesting to put the two MR2s around the same track and see what happened. ISTR reading about how a Mini with an A series engine but 8 port head was quicker around the track than the XE and Honda engined ones supposedly because it was better balanced - not more powerful I'd love to know more about the 400bhp escorts. Are they 4wd? What's their chassis setup? In my fantasy project land, I'd like to build something like a Minor or A40 with the mechanicals of a nice FWD car mid-engined where the back seats are. My thinking is that to get a V6 or V8 in the front is going to need a lot of cutting to move the engine back far enough to get the balance and even then the rear is going to be very light and lose traction easily. FWD V6's are readily available, no mixing and matching of axles, gearboxes and suspension to get it all to work, just a case of sorting out the gear linkage. Oh and cutting out a big hole and welding in the FWD subframe plus strengthening  This seems logical in my head but not many people seem to be doing it so perhaps it's just a nightmare in real life. |
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Apr 12, 2007 10:01:04 GMT
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Suspension setup is crucial. My mini will torque steer like its on rails (wavy ones) because the camber/caster/toe/height is not set. Also the scrub radius is large and the steering is heavy. All these can be largly overcome with the right setup, lower off-set wheels, metro hubs and powersteering, then the 180hp goes in a straight line !! Mini's torque steer due to unequal length drive shafts, the same as most? front wheel drive cars. It can be sorted with special diffs/driveshafts but its pricey (or at least it was when i looked 10 years ago) |
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Apr 12, 2007 10:20:55 GMT
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Not really a factor on mine, although not exactly equal it does have the dummy shaft from the Astra (XE). It's more to do with extreme amounts of torque showing up the weakness in the other areas. Actually power steering is reckoned to be one of the best 'quick' fixes available.
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stealthstylz
Club Retro Rides Member
Posts: 14,954
Club RR Member Number: 174
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Power to weight or size ratiostealthstylz
@stealthstylz
Club Retro Rides Member 174
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Apr 12, 2007 10:36:20 GMT
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I've always thought of it like this in terms of how dangerous a car is to drive FWD - Can have too much power in a straight line and cornering - e.g. mates old mk2 fester turbo, running silly power ~ 300bhp + nitrous, used to torque steer from one side of the road to the other when you nailed it. Understeered like curse word everywhere making it very difficult to drive - On a road with corners my old clio 16v was quicker point to point. RWD - Can have too much power for cornering (especially turboed) - e.g. Even though too much power will make the wheels spin, it'll still go in a relatively straight line and be easy to drive. However on corners can bite you in the  if theres too much power especially in the wet and with big turbos where you have a high spool rpm - mate had a 200sx with a t4 turbo on, used to handle great at high speed, but on low speed corners the boost would kick in so hard it span. No way to cure it apart from to wait till you were all way round the corner until you booted it. Matt |
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Apr 12, 2007 10:59:42 GMT
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^ Maybe i might but that turbo idea on hold, well it is on hold anyway!
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it doesn't matter if it's a Morris Marina or a Toyota Celica - it's what you do with it that counts |
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Apr 12, 2007 11:51:26 GMT
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Mini's torque steer due to unequal length drive shafts, the same as most? front wheel drive cars. I thought minis had equal length shafts. |
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Apr 12, 2007 12:42:43 GMT
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It's all in the delivery, my cbr600 redlines at 13000rpm and it's so smooth all the way its boring
It has 380bhp/tonne. I think it's slow. If it made 380b/t with a turbo squezzed into a 6000rpm
rev range it would be all different again.
Mates hayabusa has a bout 760bhp/tonne. 'almost' boring.
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Apr 12, 2007 12:54:52 GMT
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It's all in the delivery, my cbr600 redlines at 13000rpm and it's so smooth all the way its boring It has 380bhp/tonne. I think it's slow. If it made 380b/t with a turbo squezzed into a 6000rpm rev range it would be all different again. Mates hayabusa has a bout 760bhp/tonne. 'almost' boring. Not wth you on board it doesnt ;D ;D It wont ride itself so Power to weight is whatever Honda quote as a Dry weight + 30KG to bring it up wet + Your weight in your Leathers and helmet Bet its no where near 380hp/tonne then ;D |
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Apr 12, 2007 13:29:42 GMT
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Good thinking! I wonder exactly how much original design takes into consideration one person (7-30 stone? ) sat on oneside of the car on his/her bill for much of the time. |
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it doesn't matter if it's a Morris Marina or a Toyota Celica - it's what you do with it that counts |
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Apr 12, 2007 13:47:55 GMT
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According to my almost certainly flawed calculations my car has 192bhp/tonne.
However i'm more confident in saying that power wouldn't make it any quicker round a track. ;D
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Apr 12, 2007 13:54:57 GMT
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still about 300b/t either way my point is the delivery is what makes it "fast but boring"/ "slow but exciting" my bike would be about 320b/t if i got off my and fixed the camchain, or even got me a cbr900 to squeeze in (400b/t) anyway back o/t now! |
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Apr 12, 2007 14:05:22 GMT
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This seems logical in my head but not many people seem to be doing it so perhaps it's just a nightmare in real life. 
