Cars pulling away from me on the straights (PP restricted racing)
- Thread starter chuyler1
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chuyler1
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- chuyler1
Ok, so I've been looking at three cars lately to crack this performance point thing. I'd like to be able to look at a car and determine whether it is a good candidate BEFORE I spend several 100k on modding it for pp racing.
Car 1 is a N/A '86 MR2 with a stage 3 turbo
Car 2 is a '86 MR2 SC with an upgraded supercharger
Car 3 is a '99 MR-S with a stage 3 turbo
Car 1 and 2 run fairly similar lap times but car 3 is upwards of 2-3 seconds quicker on a course like Trial Mountain. At first glance it makes no sense since car 1 has a better kg/HP rating. However the graphs reveal a little more when you filter by power band. Car 1 is very peaky and torque and hp drop off quickly as you near redline. Car 2 needs to be run in manual mode since it is pointless to run to redline when you have more torque at the same hp level at lower rpms. Car 3 has a much broader curve in the power band and doesn't lose as much high end torque as rpms increase. The differences are subtle but it really makes a difference on a course like Trial Mountain where you need a strong power band to maximize speed on the uphill portions of the track.
Car 1 is a N/A '86 MR2 with a stage 3 turbo
Car 2 is a '86 MR2 SC with an upgraded supercharger
Car 3 is a '99 MR-S with a stage 3 turbo
Car 1 and 2 run fairly similar lap times but car 3 is upwards of 2-3 seconds quicker on a course like Trial Mountain. At first glance it makes no sense since car 1 has a better kg/HP rating. However the graphs reveal a little more when you filter by power band. Car 1 is very peaky and torque and hp drop off quickly as you near redline. Car 2 needs to be run in manual mode since it is pointless to run to redline when you have more torque at the same hp level at lower rpms. Car 3 has a much broader curve in the power band and doesn't lose as much high end torque as rpms increase. The differences are subtle but it really makes a difference on a course like Trial Mountain where you need a strong power band to maximize speed on the uphill portions of the track.
- 139
You have two straights at trial mountain where that 252 hp comes into play. You have to select your cars based on the track. Your garage needs to be tailored for specific types of tracks. Car 2 should be better at Tsukuba and Eiger short track provided that you set the transmission correctly.
- 2,083
- FreedomWeasel
chuyler1
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yeah, as i was compiling the photos I thought of that too. I've driven it in manual but always to redline (~8,500rpm). I didn't try setting up the transmission for running between say 6,000rpm and 7,500rpm. I see now that it is better to use the uphill slope on that graph before max hp than the downhill slope since there is more torque available on the uphill. I'll try that tonight and see if it'll run faster than the MR-S...but I typically don't do well in manual with cars that have a narrow band. It takes many laps to get the shift points just right.
I went down the list of cars I currently own to do some more comparisons. The hondas that seem so fast on the track all hit peak hp just before redline. I think that is the secret. Shift at or just after peak hp so you don't get stuck on the low-torque downward slope. Then optimize the transmission for hitting top speed at or just before peak hp rpm so when you reach 6th gear you don't too into no-torque land.
I went down the list of cars I currently own to do some more comparisons. The hondas that seem so fast on the track all hit peak hp just before redline. I think that is the secret. Shift at or just after peak hp so you don't get stuck on the low-torque downward slope. Then optimize the transmission for hitting top speed at or just before peak hp rpm so when you reach 6th gear you don't too into no-torque land.
chuyler1
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- chuyler1
This is very true, but Trial Mountain is tricky. I've tried heavier high hp cars and they don't run any quicker on the straights. In fact they are more often than not slower. However going too light doesn't help either. The kg/HP rating is not a good gauge so the secret formula is within the power curves. You want lots of power where you need it, and no power where you don't so that you can get the most hp per performance point.
- 448
Gears work by multiplying torque, and the shorter a gear is the more it multiplies torque.
EDIT - As far as your second point, that gets tricky. If a gear is shorter, it'll multiply torque more, but making the gearing too short so that you move out of your powerband would mean that you're multiplying less torque...kinda confusing. I'd play around with settings and see what works. You can figure it out mathmatically but it'll probably be less work just to see what feels best.
EDIT #2 - http://www.car-videos.net/articles/horsepower_torque.asp
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chuyler1
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Ok, I know you basically want to run the shortest gears possible for a given track but you also want to keep the car at its power band for as long as possible. To run the 2nd MR2 at lower rpms I have to set the transmission top speed at like 162 even though I'm only going to hit 125...but it means I hit 125 at 6,000rpm. But for the 1st car, I set the transmission top speed at 137 and it will bounce off the limiter if I go over 130. Both cars hit 125 at the same place on the track.
I came to this conclusion after trying to run the 2nd car with the 137 transmission setting. I shift through gears 2-5 really fast and then cruise around in 6th the whole time. It was a lot of work shifting whenever I slowed down and I inevitably ended up outside my desired power band.
So now I just make sure when I reach top speed on a track, the tach at the top end of the power band. It has been working pretty good so far but i'm sure there is room for improvement if I were to customize each ratio.
I came to this conclusion after trying to run the 2nd car with the 137 transmission setting. I shift through gears 2-5 really fast and then cruise around in 6th the whole time. It was a lot of work shifting whenever I slowed down and I inevitably ended up outside my desired power band.
So now I just make sure when I reach top speed on a track, the tach at the top end of the power band. It has been working pretty good so far but i'm sure there is room for improvement if I were to customize each ratio.
- 139
Chuyler, you seem to be floundering a little. Use oppositelock's spreadsheet. He provides gear calculations and suggested shift points. You just have to enter the cell data. Makesure you download the read me file as well.
https://www.gtplanet.net/forum/showthread.php?t=168122&page=3
Nevermind Chuyler. I noticed that you are already familar with the sheet.
https://www.gtplanet.net/forum/showthread.php?t=168122&page=3
Nevermind Chuyler. I noticed that you are already familar with the sheet.
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- 863
- oops_sorryy
How does the SC MR2 do when you don't upgrade the Supercharger? I noticed when ou take the upgraded one of my peak power jumps way up on the RPM band. Maybe that's the key to the SC edition, don't upgrade the Supercharger, but everything else? I'm going to try to get my hands on a another one and test it out.
chuyler1
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i've tried upgraded SC vs non upgraded SC. Not too much of a difference, I still prefer the turbo version.
I just ran some more laps and messed with the LSD settings. I guess since I'm not spinning the tires (racing tires) I can lower the accel number. That helped a little bit with some turn in, and I also lowered the brake value. Felt better but might have had minimal effect.
Then I pulled out a '95 NSX. Pretty much stock to get 450pp. Ran a few laps with stock LSD and stock suspension and layed out a 1:31.7 on my 2nd lap. It was tough to handle with the stock suspension though. I installed the custom suspension and used the GT5 quicktune spreadsheet for some initial settings. 1:31 flat and there's at least another second to be had but the front stretch was tough to manage. But the car just revs so much smoother.
In any case, i'm slowly coming to the conclusion that some cars are just going to be faster than others. The PP system is skewed in favor of certain cars.
Looking at the NSX graph, I think I know what to look for in other cars. A relatively flat torque curve (no extreme drops on either side of peak) along with a HP curve that shoots up at 45 degrees until peak. My MR-S is pretty decent because torque doesn't drop off dramatically and hp builds gradually. My Mazdaspeed Atenza is horrible because the torque curve is midrange biased and the hp is high-end biased. There is no way to tune it so you get both hp and torque within the same band. I've tried lots of tricks with the power limiter and the best I can do is about 1:34 at Trial Mountain.
I just ran some more laps and messed with the LSD settings. I guess since I'm not spinning the tires (racing tires) I can lower the accel number. That helped a little bit with some turn in, and I also lowered the brake value. Felt better but might have had minimal effect.
Then I pulled out a '95 NSX. Pretty much stock to get 450pp. Ran a few laps with stock LSD and stock suspension and layed out a 1:31.7 on my 2nd lap. It was tough to handle with the stock suspension though. I installed the custom suspension and used the GT5 quicktune spreadsheet for some initial settings. 1:31 flat and there's at least another second to be had but the front stretch was tough to manage. But the car just revs so much smoother.
In any case, i'm slowly coming to the conclusion that some cars are just going to be faster than others. The PP system is skewed in favor of certain cars.
Looking at the NSX graph, I think I know what to look for in other cars. A relatively flat torque curve (no extreme drops on either side of peak) along with a HP curve that shoots up at 45 degrees until peak. My MR-S is pretty decent because torque doesn't drop off dramatically and hp builds gradually. My Mazdaspeed Atenza is horrible because the torque curve is midrange biased and the hp is high-end biased. There is no way to tune it so you get both hp and torque within the same band. I've tried lots of tricks with the power limiter and the best I can do is about 1:34 at Trial Mountain.
- 40
What people miss is hp IS torque. Hp=torque x rpm / 5252. That's where you can make a distinction. Using a previous example, you can make the 200hp/400ft-lb car just as quick in a straight line as the 400hp/200ft-lb simply with gearing. One problem I've seen with the gran turismo franchise is that it seems to favor newer cars. In most cases the same model of car that's just older can't handle as well or make as much power as the newer version of the same car. The pp system tries to fix that, but it doesn't work very good at it.
- 864
- NorCal
- oppositelock27
That's false. Using gearing you can make a 400hp/200lb-ft car as fast as a 400hp/800lb-ft car or vice versa.
- 1,945
- Treviglio
- PAPPACLART
- PAPPALCART
Bhp and torque are the same thing. Bhp is born from torque multiplied by rpm; so
as torque and Bhp are the same then they are both just as important as each other in terms of acceleration.
I have 2 cars both with 266bhp and both 1170kg. One is a 120d, the other an s2000. The 120d has twice the torque but does not accelerate twice as fast as the s2000. The reason why the s2000 accelerates as fast as the 120d despite having half the torque is simply because it produces its power at roughly double the rpm peak of the 120d which allows the s2000 to run gearing half that of the more torquey 120d. Gear ratios are a multiplier torque, and an engines ability to rev allows it to run lower gearing, further multiplying the torque the engine produces.
Take a look at a thrust curve, its the best illustration of a vehicles in gear acceleration. Be amazed at how it is possible for an NA 2000cc engine to have equal or more thrust than an engine twice its size because it can rev twice as hard.
A current 2.4 f1 engine has only approx 210 lbs of torque, but It will have more in gear thrust at anyv speed then most big motors twice its size, and its all down to the fact that a more f1 car can rev to 18000rpm.
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- 379
- PNW
- Zenmervolt
No. The car with 400 ft-lbs of torque and 200 hp will be running out of steam at very low RPM. Remember, HP = TQ*(RPM/5252). A car with 400 ft-lbs of torque and only 200 peak hp will have its power peak at only 2,626 RPM, and practical engineering concerns mean it will pretty much be dead above 3,500 RPM.
A car with 200 ft-lbs of torque and 400 hp will be hitting peak power at 10,504 RPM.
The second car will be able to take advantage of gearing. Cut the gear ratio in half and you double the torque to the wheels and it's torque at the wheels that matters.
If we give both engines the same gear ratios, the second engine will still be just barely ready to hit 2nd gear at the same speed where the "high torque" engine has just shifted into 4th! Because of the massive advantage from the lower gearing's torque multiplication at the wheels being used for a much longer time, the car with less torque will actually be faster; in fact it will be significantly faster.
For a good read on HP and Torque that goes into more detail than I do here, I strongly recommend this link: http://www.vettenet.org/torquehp.html
chuyler1
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- chuyler1
So I have put away my MR2s for a bit to get a feel for faster cars. Last night I spent several hours with some of my buddies tuning 450pp cars at Trial Mountain.
My '95 NSX is lightning fast with just an air filter. After some tuning it was running low 1:30s with an occasional 1:29. It only has a 5spd tranny but man does it pull hard in every gear and it brakes and corners on rails. Puts my over-modded MR2s to shame in every category.
Next up was the RX8. Quite a different experience compared to the NSX. I was working the gears like crazy letting that engine scream. 8500 rpm was the sweet spot for max torque/hp on the uphill but occasionally I let it run up to 9000. Once I got familiar with the new shift points I was running consistent 1:29s.
Now it was time for my IRL car, the Mazdaspeed Atenza. I added full weight reduction but the car is still pretty heavy. Weight reduction left no points for mods and I had to use a little more performance reduction than the other cars. This car was just plain slow. I could not break into the 1:31s. The car has plenty of torque and it corners pretty well, it just wouldn't accelerate out of the turns or up the hill.
A good gauge on Trial Mountain is the top speed just before cresting the hill at the top of the course. Good 450pp cars will hit 124-128. Sluggish cars will have trouble breaking 120-122. The Mazdaspeed Atenza barely hit 119. I spent a good hour messing with gear ratios and over-modding + performance reduction. Nothing would get that car to hit 124 up the hill.
Later in the evening I ran some races in the RX8. Boy is it slow off the line (no low end torque) but once you get up to 8,000 rpm it's a screamer and I was pulling on other drivers. I had enough power to pass on the outside of the cape ring sweepers.
So I think it really comes down to trial and error with a given PP level. Some cars are just going to be quicker due to more racing oriented power curves.
My '95 NSX is lightning fast with just an air filter. After some tuning it was running low 1:30s with an occasional 1:29. It only has a 5spd tranny but man does it pull hard in every gear and it brakes and corners on rails. Puts my over-modded MR2s to shame in every category.
Next up was the RX8. Quite a different experience compared to the NSX. I was working the gears like crazy letting that engine scream. 8500 rpm was the sweet spot for max torque/hp on the uphill but occasionally I let it run up to 9000. Once I got familiar with the new shift points I was running consistent 1:29s.
Now it was time for my IRL car, the Mazdaspeed Atenza. I added full weight reduction but the car is still pretty heavy. Weight reduction left no points for mods and I had to use a little more performance reduction than the other cars. This car was just plain slow. I could not break into the 1:31s. The car has plenty of torque and it corners pretty well, it just wouldn't accelerate out of the turns or up the hill.
A good gauge on Trial Mountain is the top speed just before cresting the hill at the top of the course. Good 450pp cars will hit 124-128. Sluggish cars will have trouble breaking 120-122. The Mazdaspeed Atenza barely hit 119. I spent a good hour messing with gear ratios and over-modding + performance reduction. Nothing would get that car to hit 124 up the hill.
Later in the evening I ran some races in the RX8. Boy is it slow off the line (no low end torque) but once you get up to 8,000 rpm it's a screamer and I was pulling on other drivers. I had enough power to pass on the outside of the cape ring sweepers.
So I think it really comes down to trial and error with a given PP level. Some cars are just going to be quicker due to more racing oriented power curves.
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- 863
- oops_sorryy
Right now I'm trying to tune the tranny for the power band of the MR2 '86. I usually race sports soft, but I'll slap on some Racing Softs and see what times I can post with these new tranny settings.
