I give up. ( Track vid and slips inside )
11-01-2016, 02:00 PM
#61
Here's a simplified comparison that might help illustrate where i'm coming from-
Your no boost 6500 rpm launch likely drops to around 3500 by .7 seconds in, which lowers the average rpm to around 5000 or about 58.33 revolutions over .7 sec.
A 5500 rpm launch without any rpm drop at all will have a 5500 rpm average over those same .7 seconds, or about 64.16 revolutions...about a 10% gain in power production over the first .7 sec.
After that initial .7 sec, the 6500 rpm launch begins it's climb from 3500 because of the bog. Over the next .3 sec it will average around 3650 rpm, or 18.25 revolutions, for a total of around 76.58 revolutions of power production over the 1st second of the run. The 5500 rpm launch without any bog will average 5500 rpm over the same time period, or about 91.66 revolutions of power production. With roughly 20% more revolutions of power production during the first second of the run, the 5500 rpm no boost launch with controlled clutch slip is going to spool the turbo much quicker than the typical 6500 rpm no boost launch.
If you simply took clutch out of the car until you could launch no-boost without losing rpm, there's no way that clutch would be able to hold when the car starts making power. Temporarily holding back some clutch clamp pressure makes it possible to slip more initially to raise average rpm, but also have enough clamp in reserve to hold the power down the track.
Your no boost 6500 rpm launch likely drops to around 3500 by .7 seconds in, which lowers the average rpm to around 5000 or about 58.33 revolutions over .7 sec.
A 5500 rpm launch without any rpm drop at all will have a 5500 rpm average over those same .7 seconds, or about 64.16 revolutions...about a 10% gain in power production over the first .7 sec.
After that initial .7 sec, the 6500 rpm launch begins it's climb from 3500 because of the bog. Over the next .3 sec it will average around 3650 rpm, or 18.25 revolutions, for a total of around 76.58 revolutions of power production over the 1st second of the run. The 5500 rpm launch without any bog will average 5500 rpm over the same time period, or about 91.66 revolutions of power production. With roughly 20% more revolutions of power production during the first second of the run, the 5500 rpm no boost launch with controlled clutch slip is going to spool the turbo much quicker than the typical 6500 rpm no boost launch.
If you simply took clutch out of the car until you could launch no-boost without losing rpm, there's no way that clutch would be able to hold when the car starts making power. Temporarily holding back some clutch clamp pressure makes it possible to slip more initially to raise average rpm, but also have enough clamp in reserve to hold the power down the track.
11-01-2016, 02:04 PM
#62
What were you launching at and how were you doing the clutch? I only went that one time that I got a 10.80 out of mine but it didn't feel like it would 60 ft much better than what I was getting, maybe could have dropped into the 1.70s with a tad more rpm but that was around a 5k slip/dump.
I do have a fairly small turbo, T4 78mm so it spools up pretty fast once I start moving. I think the OP has the same turbo or did at one point?
11-01-2016, 04:17 PM
#65
And here's where I'm coming from, with a 2 step I can launch at less rpm with more power than you could ever hope to generate launching at any rpm regardless of whether rpms drop or not at whatever rpm you want. Slipping the clutch also wears out the clutch matrial sooner.
I think you may overlooking the effect of rpm drop on the launch. Any time you have a WOT drop in rpm, that's an indicator that you released inertia energy from the rotating assembly into the drivetrain. This is the energy that a grabby clutch pulls out of your 100lb or so rotating assembly to hit the drivetrain with. But it's a give/take/take thing though...it borrows energy to hit the drivetrain/tires artificially hard, so you then must over-build the drivetrain to accommodate that surge, which slows you down overall. Then as your car recovers lost rpm, it takes again as you gain speed at a slower rate until that borrowed energy is paid back in full.
If you want to stick radials with a manual, rpm drop is your enemy. When your launch does not include rpm drop, the hit is much less violent. A less violent hit requires less shock control, which in turn makes the car less likely to kick the tires loose when you encounter bumps down the track.
Added wear to the clutch is less than you would think. My personal street/strip car isn't turbo, but currently has a 2800lb diaphragm with a 10.4" solid hub full face 5135 iron disc. It NEEDS that much clamp to hold 800ft/lbs for those times when the little 355 gets both kits turned on. But as you can imagine, that much clamp on an iron disc is going to hit pretty hard. Now imagine me trying to launch naturally aspirated or maybe just one kit with that much clamp on an iron disc...not pretty without the ability to dial out some clutch. When i was at 700whp I used a 900 series segmented iron disc and that lasted 2-3 years with about .5 to .7 seconds of WOT slip. But here's the thing- the car gets faster the longer i let the clutch slip. For me personally, dialing in 1 second of slip is a good compromise that puts me in the comfortable position of a clutch disc lasting a full season without needing maintenance. I'm mostly a no-prep guy, so smooth power delivery and being able to add power as i work my way thru the gears is big to me. Can’t do that with a typical adjustable set for a good launch, as bringing on more power down the track just blows thru the clutch.
11-01-2016, 06:04 PM
#67
I feel that if the budget is tight, the op will get farther adding clutch slip before 2 step, as clutch slip can net the him a better 60' while reducing the need for an upgraded rear. He can combine clutch slip with a 2 step later when he gets a rear that can handle it, but adding 2 step on a Stage 5 without adding some slip will kill his 10 bolt.
11-01-2016, 06:25 PM
#68
I feel that if the budget is tight, the op will get farther adding clutch slip before 2 step, as clutch slip can net the him a better 60' while reducing the need for an upgraded rear. He can combine clutch slip with a 2 step later when he gets a rear that can handle it, but adding 2 step on a Stage 5 without adding some slip will kill his 10 bolt.
11-01-2016, 09:21 PM
#69
Before sticking a boring TH400 in it I think you should put a rear worthy of some abuse and send it on proper tire. It will make all the difference if you drive it correctly!
Driving it correctly is key as it seems some in this thread cant get a car off the line to save their lives. My first trip to the track after my trans swap (from a TH400 to TR-6060) I ran 1.5-1.6 60' in a turbo car that weighs in over 4k lbs and I don't have a two step. I didn't need to launch at 6500RPM either but I did have to lower my tire pressure and it went 10's on wastegate with a chinese turbo with a kids seat in the back. I have a 3.45 rear with a 295 Hoosier DR.
While I am looking to hookup a 2 step and improve my 60' I wouldn't say its critical to making a manual car 60' decently. I would put a proper tire on it and learn how to drive it first, then improve by adding boost off the line.
Driving it correctly is key as it seems some in this thread cant get a car off the line to save their lives. My first trip to the track after my trans swap (from a TH400 to TR-6060) I ran 1.5-1.6 60' in a turbo car that weighs in over 4k lbs and I don't have a two step. I didn't need to launch at 6500RPM either but I did have to lower my tire pressure and it went 10's on wastegate with a chinese turbo with a kids seat in the back. I have a 3.45 rear with a 295 Hoosier DR.
While I am looking to hookup a 2 step and improve my 60' I wouldn't say its critical to making a manual car 60' decently. I would put a proper tire on it and learn how to drive it first, then improve by adding boost off the line.
What were you launching at and how were you doing the clutch? I only went that one time that I got a 10.80 out of mine but it didn't feel like it would 60 ft much better than what I was getting, maybe could have dropped into the 1.70s with a tad more rpm but that was around a 5k slip/dump.
Last edited by Game ova; 11-01-2016 at 09:38 PM.
11-01-2016, 09:46 PM
#70
...when you combine the two you make even more power in a tighter time frame.
I think you may overlooking the effect of rpm drop on the launch. Any time you have a WOT drop in rpm, that's an indicator that you released inertia energy from the rotating assembly into the drivetrain. This is the energy that a grabby clutch pulls out of your 100lb or so rotating assembly to hit the drivetrain with. But it's a give/take/take thing though...it borrows energy to hit the drivetrain/tires artificially hard, so you then must over-build the drivetrain to accommodate that surge, which slows you down overall. Then as your car recovers lost rpm, it takes again as you gain speed at a slower rate until that borrowed energy is paid back in full.
If you want to stick radials with a manual, rpm drop is your enemy. When your launch does not include rpm drop, the hit is much less violent. A less violent hit requires less shock control, which in turn makes the car less likely to kick the tires loose when you encounter bumps down the track.
Added wear to the clutch is less than you would think. My personal street/strip car isn't turbo, but currently has a 2800lb diaphragm with a 10.4" solid hub full face 5135 iron disc. It NEEDS that much clamp to hold 800ft/lbs for those times when the little 355 gets both kits turned on. But as you can imagine, that much clamp on an iron disc is going to hit pretty hard. Now imagine me trying to launch naturally aspirated or maybe just one kit with that much clamp on an iron disc...not pretty without the ability to dial out some clutch. When i was at 700whp I used a 900 series segmented iron disc and that lasted 2-3 years with about .5 to .7 seconds of WOT slip. But here's the thing- the car gets faster the longer i let the clutch slip. For me personally, dialing in 1 second of slip is a good compromise that puts me in the comfortable position of a clutch disc lasting a full season without needing maintenance. I'm mostly a no-prep guy, so smooth power delivery and being able to add power as i work my way thru the gears is big to me. Can’t do that with a typical adjustable set for a good launch, as bringing on more power down the track just blows thru the clutch.
I think you may overlooking the effect of rpm drop on the launch. Any time you have a WOT drop in rpm, that's an indicator that you released inertia energy from the rotating assembly into the drivetrain. This is the energy that a grabby clutch pulls out of your 100lb or so rotating assembly to hit the drivetrain with. But it's a give/take/take thing though...it borrows energy to hit the drivetrain/tires artificially hard, so you then must over-build the drivetrain to accommodate that surge, which slows you down overall. Then as your car recovers lost rpm, it takes again as you gain speed at a slower rate until that borrowed energy is paid back in full.
If you want to stick radials with a manual, rpm drop is your enemy. When your launch does not include rpm drop, the hit is much less violent. A less violent hit requires less shock control, which in turn makes the car less likely to kick the tires loose when you encounter bumps down the track.
Added wear to the clutch is less than you would think. My personal street/strip car isn't turbo, but currently has a 2800lb diaphragm with a 10.4" solid hub full face 5135 iron disc. It NEEDS that much clamp to hold 800ft/lbs for those times when the little 355 gets both kits turned on. But as you can imagine, that much clamp on an iron disc is going to hit pretty hard. Now imagine me trying to launch naturally aspirated or maybe just one kit with that much clamp on an iron disc...not pretty without the ability to dial out some clutch. When i was at 700whp I used a 900 series segmented iron disc and that lasted 2-3 years with about .5 to .7 seconds of WOT slip. But here's the thing- the car gets faster the longer i let the clutch slip. For me personally, dialing in 1 second of slip is a good compromise that puts me in the comfortable position of a clutch disc lasting a full season without needing maintenance. I'm mostly a no-prep guy, so smooth power delivery and being able to add power as i work my way thru the gears is big to me. Can’t do that with a typical adjustable set for a good launch, as bringing on more power down the track just blows thru the clutch.
11-02-2016, 10:17 AM
#71
I agree, that would be cool to do a comparo on.
You've definitely made a good case with the slipper device data. But being that this clutch cost close to $1,000 I try to keep slip to a minimum. In an attempt to break into the sub 2.0 60' realm I did try and ride the clutch once....and the thing STILL went a 2.1x.
You've definitely made a good case with the slipper device data. But being that this clutch cost close to $1,000 I try to keep slip to a minimum. In an attempt to break into the sub 2.0 60' realm I did try and ride the clutch once....and the thing STILL went a 2.1x.
If you could get some rpm data it would be easier to pinpoint exactly where you are going wrong with your current slipping efforts. You don't need a racepak, just anything that can generate an rpm graph would be well worth the effort. Something as simple as a Gtech can get the job done, might be some phone apps out there as well.
11-02-2016, 03:00 PM
#72
My car ran great with the TH400 it was just boring, mash the gas and it would run 9's without even trying. But the car would literally sit for weeks between startups because I had no desire to drive it with the auto, came down to either manual swap or get rid of it. Now with the manual I find reasons to go hoon it all the time and always come back with a **** eating grin. I wouldn't go back to auto for anything other then a purpose built drag car.
2500 is way too low to launch and you need a little slip when not using a 2 step to get load on the engine so turbo spins up.
11-02-2016, 03:05 PM
#73
My car ran great with the TH400 it was just boring, mash the gas and it would run 9's without even trying. But the car would literally sit for weeks between startups because I had no desire to drive it with the auto, came down to either manual swap or get rid of it. Now with the manual I find reasons to go hoon it all the time and always come back with a **** eating grin. I wouldn't go back to auto for anything other then a purpose built drag car.
2500 is way too low to launch and you need a little slip when not using a 2 step to get load on the engine so turbo spins up.
2500 is way too low to launch and you need a little slip when not using a 2 step to get load on the engine so turbo spins up.
11-02-2016, 03:43 PM
#74
I expect once I turn the boost up and hook the 2 step up the manual will come together to narrow the gap.
11-04-2016, 02:06 PM
#75
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I love the idea of running a Th400 and laying down the law at the track, but I really need to decide if I want a fast track car....or a fun street car. And talking about the track brings up 2 issues, I would only be able to make 1..maybe two passes out the back door because I don't have a cage....and won't be installing one either (No safety speech needed). And the other issue, I have yet to see a 4th gen with a Th400 swap make the shifter look like it "belongs"....true it's cosmetic and isn't really serious...but still. Speaking of cage, the guy that I mentioned earlier that swapped to the Th400 from the t56 and now runs 9.40 @150 just ran into this very issue. After his last pass (first run out the back).....they told him to come to the tower. His days are now numbered track wise......