Power to Weight VS actual acceleration

XDesperado67 · May 31, 2011

Why won't some cars accelerate at a reasonable rate despite having an incredibly high Power to Weight ratio.
This is not an issue of wheel spin and the cars have good torque in the useable power band.

Example: Gianetti G4 fully modified with medium turbo has 277 bhp 270 ft/lb torque and weighs 416 kg. Assuming that you get little to no wheel spin it should accelerate like a rocket and yet the reverse is true with it actually being fairly sluggish with a much lower than expected top end.

kickin_on · May 31, 2011

My guesses are the age of the technology in the car in general, and/or crappy gear ratios...

XDesperado67 · May 31, 2011

kickin_on
My guesses are the age of the technology in the car in general, and/or crappy gear ratios...

I put a racing transmission in it and have tried a variety of gear ratios. I'm sure that my using automatic transmission doesn't help but don't think it should be this bad and still doesn't explain the low top end. It makes a Lotus 111R look like a drag racer :sly:

And by the way this isn't the only car I've seen this issue with.

Corpsey · May 31, 2011

The engine is too small and only 2 valves per cylinder.. I would say take it around grand valley east with low rpm turbo and mid rpm turbo and see what's better for accelerating.. Also, if you have the custom transmission, try lengthier lower gears and taller higher gears. This way you'll be putting more power into the wheels at a steadier pace until you get to your higher gears (where you don't need to have torque anymore)

Basically what kickin_on said

The 111r has doubly more valves per cylinder.....

kickin_on · May 31, 2011

Hmmm... Maybe try posting this in the Tuning section? Might get better info there?

Edit: Not to imply that Corpsey's response wasn't good info lol...

chris speed · May 31, 2011

Try soft racing tires maybe??

Space Dynamics · May 31, 2011

Crappy powerband.

oopssorryy · May 31, 2011

Acceleration has many factors, transmission gearing, aero dynamics (natural and wing created), power to weight, and engine response. The G4's biggest let down (IMO) that you can't change is the two valves per cylinder as previously stated. The more valves you have (so cars have up to five) that better engine response because you taking in and expelling air at a much faster rate.

You just have to figure out the right gearing, might take a while, but it's doable. The low RPM turbo (as others have said) will give you much more response than the High RPM Turbo, if you rally can't figure this car out, change to it.

Skunkyskunkface · May 31, 2011

More valves may give you better engine response but he is talking about a fully tuned ginetta that using the valves it has got produces so much power and does nit accelerate similarly compared other vehicles. Adding more valves may make the car more responsive, smoother and more powerful but this car (and others) should accelerate faster than it does. I feel the caterham is similar. I think that ultra lightweight cars are badly replicated by the game.

dr_slump · May 31, 2011

What are you guys talking about?
An engine with 250hp/400lb has 250hp/400lb, doesn't matter if it's an engine with 2 or 4 valves.

In my opinion, the tires spin. The tires won't get red, but they still spin. This happens especially with superlight cars.

Make a try with SRF on (and full locked diff) and compare it with SRF off. You'll see....

Corpsey · May 31, 2011

Wiki: "Multivalve engines normally produce maximum torque (and power) at relatively high speeds compared to two-valve designs."

All I was suggesting is that the cars torque may not be what the OP wants..

Adrenaline · May 31, 2011

Power to weight is only a part of the equation.
Where, when and for how long the car makes that power, is another large part of that equation. (As well as where the weight is)
Basically, What do the power bands look like?

PAPPACLART · May 31, 2011

I think the Ginetta G4 is quite peaky so that can hurt acceleration, especially in a 5 speed box, but still, with 277 BHP and only 416kgs it should still accelerate like a superbike at least up until 130mph traction permittig.

I have notcied this with some of the light cars, it seems that PD have got some for there calculations wrong.

Corpsey · May 31, 2011

I think the problem is that there's no real tire temperature... you can't warm your tires up pre-launch..

Adrenaline · May 31, 2011

Corpsey
I think the problem is that there's no real tire temperature... you can't warm your tires up pre-launch..

I disagree with this somewhat.
I spent a night making a Drag car.
Launch 1 and 2 I got too much grip and bogged down the motor, but on the 3rd launch I'd get a good launch most of the time, and the 4th try I'd usually spin the tires. This is with cooling in between, so I think to a certain point temperature does come into play. But I wouldn't dare call the above experience conclusive.

Corpsey · May 31, 2011

I don't think that temperature they gain stays on them for very long though.. Are you sure you're not just talking about tire wear?

iamjajo · May 31, 2011

The engine in the G4 came out of this car. How fast do you think it's going to accelerate?

XDesperado67 · May 31, 2011

iamjajo
The engine in the G4 came out of this car. How fast do you think it's going to accelerate?

Great pic

And actually the Angling's much like the Mini's were frequent racers. They were some of the favorite "tuner"
cars of their day.

shirakawaa · May 31, 2011

XDesperado67
I put a racing transmission in it and have tried a variety of gear ratios. I'm sure that my using automatic transmission doesn't help but don't think it should be this bad and still doesn't explain the low top end. It makes a Lotus 111R look like a drag racer

And by the way this isn't the only car I've seen this issue with.

The AT mode does a very poor job on cars that have peak power at relatively low rpm, since it shift gears up at redline. This might be the reason.

TT3AZ · May 31, 2011

There settings that gives maximun weight transfer to the rear wheels, search the thread. I have my self written it on this forum.....

Rotary Junkie · May 31, 2011

Temperature is definitely part of it.

My NSX is geared in a way that on cold tires it has a pretty much perfect amount of wheelspin on a redline clutch dump... After that one launch however it bogs.

nomis3613 · May 31, 2011

Here is my 2 cents on the opening post. I don't own a G4, but at a guess:
- low speed acceleration is limited by the tyres, if they had more grip you could run shorter gearing for a quicker launch
- above a certain speed, power to weight doesn't matter much, it's more about total power. 277hp isn't a lot in the GT5 scheme of things.

XDesperado67 · May 31, 2011

Appreciate all the feedback so far. Would like to clarify my position here a bit though. I'm more concerned with mid to high end acceleration than acceleration from the standstill.
I don't drag race but I want the car (any car) that I'm using to show good acceleration from 50 or 60 mph up to its top end so you can actually pull out of corners. A car that needs half a mile to go from 60 to 130 isn't going to be to competitive, worse is not being able to goose the throttle on short straights to take advantage of position. Hate cutting a good line through a corner to overtake/pass another car only to watch them just power by making me have to repeat at next corner instead of being able to hold position and start pulling ahead.

Rekve · May 31, 2011

The lighter cars of gt5, and the electric cars as well, are imo simply handicapped in this game. Cars like the catherham and the tesla roadster are great examples of this. They should both be flying of the startline, but instead, they have rather sluggish acceleration. These cars and their sepcs have simply not been getting any, or at least not much, attention from PD as the 'normal' cars and their layouts. Possibly has something to do with the game engine or something similar.
At least that's what I think is wrong.
It's a shame really.

dr_slump · May 31, 2011

Oh forgot:

It's not important how much torque an engine has. The important thing is how much power is delivered to the wheels. Check the transmission threads.

PhillGuy · May 31, 2011

It's all about torque baby. A high power to weight in a low weight car usually means that although acceleration will be good it won't go faster than a heavier car with more torque.

It would seem that performance Points takes this into account.

XDesperado67 · May 31, 2011

PhillGuy
It's all about torque baby. A high power to weight in a low weight car usually means that although acceleration will be good it won't go faster than a heavier car with more torque.

It would seem that performance Points takes this into account.

Fully tuned the G4 makes 277bhp and 270 ft/lb torque...numbers that should make a 416 kg car accelerate like a rocket as long as the wheel spin is eliminated.

Another example is the Daihatsu Cuore XX '97 fully modified makes 209 bhp 197 ft/lb torque and weighs in the mid 600 kg range yet its acceleration is no better than other Kei cars with less bhp and torque and that weigh more. Again wheelspin isn't an issue.

AlphaGnomeo · May 31, 2011

XDesperado67
Example: Gianetti G4 fully modified with medium turbo has 277 bhp 270 ft/lb torque and weighs 416 kg.

In real life, the 195 bhp version does 0-60 in around 5 secs with a top speed of 130 mph. It may be that from 60-130 mph, drag becomes the bigger culprit.

articzap · May 31, 2011

Adrenaline
Power to weight is only a part of the equation.
Where, when and for how long the car makes that power, is another large part of that equation. (As well as where the weight is)
Basically, What do the power bands look like?

Explain how some cars are faster then others, such as Z06 vs ZR1. Z06 has way more top end and I'm not sure why. :crazy:

Adrenaline · May 31, 2011

articzap
Explain how some cars are faster then others, such as Z06 vs ZR1. Z06 has way more top end and I'm not sure why.

Gunna have to be more specific when you say 'more top end' because the last time I checked, my ZR1 has about 80 more HP than my Z06?

Power to Weight VS actual acceleration

XDesperado67

The Harvey Wallbanger

kickin_on

XDesperado67

The Harvey Wallbanger

Corpsey

kickin_on

chris speed

Space Dynamics

oopssorryy

Skunkyskunkface

dr_slump

Corpsey

Adrenaline

PAPPACLART

Corpsey

Adrenaline

Corpsey

iamjajo

XDesperado67

The Harvey Wallbanger

shirakawaa

TT3AZ

Rotary Junkie

nomis3613

XDesperado67

The Harvey Wallbanger

Rekve

dr_slump

PhillGuy

XDesperado67

The Harvey Wallbanger

AlphaGnomeo

articzap

Adrenaline

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