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SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 7:59 a.m.

In reply to stukndapast :

That's all really interesting info, but not that relevant to the OP. He will be driving a Jaguar with independent rear suspension set up primarily for autocross with moderately high power levels. 
 

He won't be lifting the wheels. 
 

And I am perfectly fine calling the speed portion of the event a "drag race". It's much easier to pronounce. cheeky

(Don't forget 80-90% of Challenge participants are not drag racers. This event is a great introduction for them. Keep it simple)

frenchyd
frenchyd UltimaDork
2/23/21 8:18 a.m.

In reply to SVreX (Forum Supporter) :

I think I'm going to listen to you since you said reaction time doesn't count, only ET.  I hope I'm not being stupid when I think 100% of the ET is the car?
    Floor it and shift at the red line. It's an automatic so how hard can that be?  Basically move the lever up a notch every time the needle gets to the red. 

Stampie (FS)
Stampie (FS) MegaDork
2/23/21 8:20 a.m.

In reply to frenchyd :

Hmmm no.  Yes easier with an automatic but I did about 10 runs in that Miata chasing 1/2 a second.  Also glad your wife is well.

rslifkin
rslifkin UberDork
2/23/21 8:36 a.m.
frenchyd said:

In reply to SVreX (Forum Supporter) :

I think I'm going to listen to you since you said reaction time doesn't count, only ET.  I hope I'm not being stupid when I think 100% of the ET is the car?
    Floor it and shift at the red line. It's an automatic so hard can that be?  Basically move the lever up a notch every time the needle gets to the red. 

If the trans shifts at a decent point on its own at WOT, I'd just let it shift.  It'll be more consistent than you shifting manually and less risk of bumping the shifter up too early or late and losing some time. 

frenchyd
frenchyd UltimaDork
2/23/21 8:58 a.m.
Stampie (FS) said:

In reply to frenchyd :

Hmmm no.  Yes easier with an automatic but I did about 10 runs in that Miata chasing 1/2 a second.  Also glad your wife is well.

I hope I don't sound ignorant but since I'm a complete newbie I'm not sure what to do to go faster than the car will let me.     If reaction time doesn't count guessing the light better won't help. 

rslifkin
rslifkin UberDork
2/23/21 9:03 a.m.
frenchyd said:

I hope I don't sound ignorant but since I'm a complete newbie I'm not sure what to do to go faster than the car will let me.     If reaction time doesn't count guessing the light better won't help. 

With an auto, it's pretty much down to just launch technique.  That's about the only place to find time driving-wise. 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 9:04 a.m.

In reply to frenchyd :

I'm not saying launch doesn't matter. Launch definitely affects ET. But reaction time does not. 
 

Yes, there are suspension things etc that can help with the launch. For a first time out, the most important thing is tires. 
 

Andrew Nelson has won the Challenge because he focused on what he is good at- drag racing.  The vast majority of other winners focused on autocross. 

 

I suspect a Jaguar V12 car should not have much trouble getting into the 13's. With a good autocross finish, that's a competitive car. Top 10 all day. 
 

Build what you are good at. Show up. Have fun. 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 9:10 a.m.
frenchyd said:
Stampie (FS) said:

In reply to frenchyd :

Hmmm no.  Yes easier with an automatic but I did about 10 runs in that Miata chasing 1/2 a second.  Also glad your wife is well.

I hope I don't sound ignorant but since I'm a complete newbie I'm not sure what to do to go faster than the car will let me.     If reaction time doesn't count guessing the light better won't help. 

By the time you reach the end of the strip, you are just sitting there letting the car do the best it can. 
 

But there are a LOT of different ways to launch, and every car is different. Some cars work better with a hard launch, some want to lock the brakes and rev the rpms to a particular level, some stage deep, some shallow, some can make it without shifting to upper gears.  My SVX has a trans controller that shifted early- it was much faster when I forced it to rev higher in every gear. 
 

There is a lot of technique to be learned in trial and error.

 

eastsideTim
eastsideTim PowerDork
2/23/21 9:25 a.m.

Another minor effect on ET is staging.  If you pull up to the line, and just barely trip the second light (If the first light goes out, you went way too far), you'll get the maximum distance between when you start moving and the start signal is tripped, so more time to accelerate.  It's not a huge factor, but it helps.

frenchyd
frenchyd UltimaDork
2/23/21 9:31 a.m.
rslifkin said:
frenchyd said:

In reply to SVreX (Forum Supporter) :

I think I'm going to listen to you since you said reaction time doesn't count, only ET.  I hope I'm not being stupid when I think 100% of the ET is the car?
    Floor it and shift at the red line. It's an automatic so hard can that be?  Basically move the lever up a notch every time the needle gets to the red. 

If the trans shifts at a decent point on its own at WOT, I'd just let it shift.  It'll be more consistent than you shifting manually and less risk of bumping the shifter up too early or late and losing some time. 

Jaguar has the transmission shifting at about 5000 rpm WOT  I'm converting it to manual shift since the redline is 6500 and with better cams  it can make power through 7000 rpm. ( the factory tested it to 8300 rpm before valve float started ) 

frenchyd
frenchyd UltimaDork
2/23/21 9:33 a.m.
eastsideTim said:

Another minor effect on ET is staging.  If you pull up to the line, and just barely trip the second light (If the first light goes out, you went way too far), you'll get the maximum distance between when you start moving and the start signal is tripped, so more time to accelerate.  It's not a huge factor, but it helps.

Thanks for the tip!  Stage deep if reaction time doesn't matter? 

eastsideTim
eastsideTim PowerDork
2/23/21 9:35 a.m.
frenchyd said:
eastsideTim said:

Another minor effect on ET is staging.  If you pull up to the line, and just barely trip the second light (If the first light goes out, you went way too far), you'll get the maximum distance between when you start moving and the start signal is tripped, so more time to accelerate.  It's not a huge factor, but it helps.

Thanks for the tip!  Stage deep if reaction time doesn't matter? 

Technically it's shallow staging.  Deep is when you go so far the first light goes off and is used when you are trying to get the best reaction time,  

frenchyd
frenchyd UltimaDork
2/23/21 9:38 a.m.
SVreX (Forum Supporter) said:
frenchyd said:
Stampie (FS) said:

In reply to frenchyd :

Hmmm no.  Yes easier with an automatic but I did about 10 runs in that Miata chasing 1/2 a second.  Also glad your wife is well.

I hope I don't sound ignorant but since I'm a complete newbie I'm not sure what to do to go faster than the car will let me.     If reaction time doesn't count guessing the light better won't help. 

By the time you reach the end of the strip, you are just sitting there letting the car do the best it can. 
 

But there are a LOT of different ways to launch, and every car is different. Some cars work better with a hard launch, some want to lock the brakes and rev the rpms to a particular level, some stage deep, some shallow, some can make it without shifting to upper gears.  My SVX has a trans controller that shifted early- it was much faster when I forced it to rev higher in every gear. 
 

There is a lot of technique to be learned in trial and error.

 

The stock Jaguar IRS is rubber mounted so on launch the wheels toe out. The first thing you do is eliminate the rubber mounts and bolt it in place.  The second thing is the stock drag link is in conflict with the arch of the axles.  To eliminate that you bring the drag link in at a 45 degree angle to pivot at the same line as the inner pivot point.  That way the suspension does what it should do and the wheels stay straight. 

frenchyd
frenchyd UltimaDork
2/23/21 9:39 a.m.

In reply to eastsideTim :

Thank you. I'm learning. 

frenchyd
frenchyd UltimaDork
2/23/21 9:43 a.m.
SVreX (Forum Supporter) said:

In reply to frenchyd :

I'm not saying launch doesn't matter. Launch definitely affects ET. But reaction time does not. 
 

Yes, there are suspension things etc that can help with the launch. For a first time out, the most important thing is tires. 
 

Andrew Nelson has won the Challenge because he focused on what he is good at- drag racing.  The vast majority of other winners focused on autocross. 

 

I suspect a Jaguar V12 car should not have much trouble getting into the 13's. With a good autocross finish, that's a competitive car. Top 10 all day. 
 

Build what you are good at. Show up. Have fun. 

Thank you for your guidance.  I'm expecting better times than that.  My tough part will be the autocross. Power won't really offset how wide and long the car is. I've never raced anything with a back seat. Or where a back seat would be. 
   But it will be a local version of the challenge. IMaybe a few other locals will show up just for fun.  If it gets enough maybe we can have a Yankees vs Rebels affair. ;-) 

Stampie (FS)
Stampie (FS) MegaDork
2/23/21 9:49 a.m.

In reply to frenchyd :

If you really get the power levels you're talking about then launch and the first 100 feet will be your hardest part.  If I were building the car you speced out my focus would be on the drag tires.  Notice in my budget post I had used autocross tires but claimed my 2 drag tires as budget exempt.   That's because I would have the best drag tires I could buy trying to get as much traction off the line as possible.  

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 11:21 a.m.

In reply to frenchyd :

There are different ways to run autocross. 
 

The general consensus is that a great autocross car runs flat, and is driven smoothly. Radius corners. A great autocross run is typically very drama free. No skidding, loss of traction, etc. 
 

But Challenge autocross runs are often different. The cars are often overpowered for their traction levels. A 10 second drag car generally has trouble cornering. So the drivers drive them differently. Instead of smooth cornering, the power is taken advantage of. You point and shoot on the straights, use all the power you've got, square the corners, then set up for the next straight and pull the trigger again. It's the opposite of "traditional" autocross driving. 
 

There are different ways to drive. 
 

The biggest challenge for you autocrossing is that your track setup will be drastically different than Gainesville.  The area in Gainesville is large, and the track setups are often nearly twice as big as typical autocross courses. It favors high powered cars (which helps the editorial content for the magazine- not every Challenge car looks like a typical autocross car). 
 

You won't find a track like that, and there will be very little similarities between the Gainesville track and the track you find. 
 

It will never be an apples to apples comparison. But you will help yourself by looking for larger autocross courses (if you can find them). Your big car with bigger horsepower will be thankful. 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 11:25 a.m.

Drag tires only matter if you have enough power to lose traction. If not, don't spend the money on them. 
 

One of the compromises you may want to consider is using 4 drag radials for BOTH events.  They will give you enough traction for drag launches, but probably also enough grip for your big car in the corners. 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 11:31 a.m.

The best way to do a comparison between 2 different autocross tracks is with a baseline car. I would suggest an I modified Miata with a nationally competitive driver. That would be pretty easy to find at lost tracks. 
 

So, if your track is a 45 second track, and the Gainesville track is a 60 second track, you can compare them as a ratio. 
 

Unfortunately, this won't help you account for the difference that may favor a big car vs the differences that may favor a small car, but it will help compare. 
 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 11:34 a.m.
frenchyd said:
rslifkin said:
frenchyd said:

In reply to SVreX (Forum Supporter) :

I think I'm going to listen to you since you said reaction time doesn't count, only ET.  I hope I'm not being stupid when I think 100% of the ET is the car?
    Floor it and shift at the red line. It's an automatic so hard can that be?  Basically move the lever up a notch every time the needle gets to the red. 

If the trans shifts at a decent point on its own at WOT, I'd just let it shift.  It'll be more consistent than you shifting manually and less risk of bumping the shifter up too early or late and losing some time. 

Jaguar has the transmission shifting at about 5000 rpm WOT  I'm converting it to manual shift since the redline is 6500 and with better cams  it can make power through 7000 rpm. ( the factory tested it to 8300 rpm before valve float started ) 

You could probably take better advantage of that with an automatic transmission and a trans controller that can program different shift points. Much more reliable shift points than a manual. 
 

But I realize you don't really want anything that is programmed. 

frenchyd
frenchyd UltimaDork
2/23/21 11:39 a.m.
SVreX (Forum Supporter) said:

In reply to frenchyd :

There are different ways to run autocross. 
 

The general consensus is that a great autocross car runs flat, and is driven smoothly. Radius corners. A great autocross run is typically very drama free. No skidding, loss of traction, etc. 
 

But Challenge autocross runs are often different. The cars are often overpowered for their traction levels. A 10 second drag car generally has trouble cornering. So the drivers drive them differently. Instead of smooth cornering, the power is taken advantage of. You point and shoot on the straights, use all the power you've got, square the corners, then set up for the next straight and pull the trigger again. It's the opposite of "traditional" autocross driving. 
 

There are different ways to drive. 
 

The biggest challenge for you autocrossing is that your track setup will be drastically different than Gainesville.  The area in Gainesville is large, and the track setups are often nearly twice as big as typical autocross courses. It favors high powered cars (which helps the editorial content for the magazine- not every Challenge car looks like a typical autocross car). 
 

You won't find a track like that, and there will be very little similarities between the Gainesville track and the track you find. 
 

It will never be an apples to apples comparison. But you will help yourself by looking for larger autocross courses (if you can find them). Your big car with bigger horsepower will be thankful. 

Very interesting. I was hoping to piggy back on one of the BMW  or Porsche events. Do Corvette clubs ever put on an Autocross ?  My thinking is they wouldn't like the tight Lotus 7/ locost  type events. 
  I realize that a 45 year old $500 junker will be outclassed by modern high dollar stuff. Plus there is no way to compare since it won't be apples to apples.  But maybe if one of the number crunchers we  seem to have so many of here could come up with some kind of handicap system?  
 

I mean I've never raced anything as big as this so I expect a lot of flying pylons. 
     
I will get a DOT set of tires. Use the stock 16x7 wheels for the auto cross and borrow/ buy a pair of drag slicks. 
 

When do I get to start whining about handicaps?;-)   I've got a good one ready  all about how high above sea level I'll be compared to Florida. Clearly that should be worth several seconds. ;-) 

Stampie (FS)
Stampie (FS) MegaDork
2/23/21 11:58 a.m.

I'd run drags in autocross tires way before I'd run autocross in drag tires.  If you are making the 400-500hp you claim you can then you will have traction issues.  I think the only good thing to come out of this discussion is I may have found the drag tires I need on CL.

Stampie (FS)
Stampie (FS) MegaDork
2/23/21 11:59 a.m.

There are DOT drag tires and DOT autocross tires that aren't recommended for use on the street.  Just saying DOT doesn't mean a lot.

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
2/23/21 12:00 p.m.
frenchyd said:I'm expecting better times than that. 

Said by literally everyone before they make a pass. Myself included after thousands of them laugh

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
2/23/21 12:03 p.m.

In reply to frenchyd :

DOT tires are not required at the Challenge.

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