07 Masters

[bullittwrench]

Ok guys need some ideas. Sat. night on a very slick surface the car was great on entry. ( a little tight but the driver prefers that ) From the center out it was terrible, not loose just wouldn't go forward. Here's what I had:
RF-400/3-5
LF-550/5-3
RR-225/94
LRF-6/0@250psi
LRR-225/4-0
5th coil-375/3-7@37" 3" travel
55%-rear
54.3%-left
100lbs LR
RUB-down 1
RLB-up1 (middle hole)
LUB-top
LLB-down1 (3rd hole up)
Long p-bar-9"on frame/bottom of pinion
RR brake caliper is on the birdcage. 414ci, 12 heads on gas, bumping the rev limiter at the end of the chutes. (8200)

The 2 main ??? I have are: Was the LLB to high causing too much loose roll steer and do I have too much gear in it for a slick track?

Thanks Guys

[MasterSbilt_Racer]

I don't believe in changing gear much. How did the car look? Was it raising up in the back? Staying flat?

I don't think the LRL is out of line. You should probably be in that hole most of the time. A combination of down one hole there and 25# more bite may be what you are looking for, but I'm not sure at this point. How much banking in the track? Fast corners or slow?

[billetbirdcage]

Do you bump the chip when the track has traction in it? When there is some traction the straight speed should be faster therefore more RPM, so if not your likely bumping the chip because of wheel spin.

[bullittwrench]

Car looked good, up on the bars. Med banked track, fast corners. We won the heat race by almost a straightaway and turned 7800. In the feature the RR tire was 2/3 used up, LR was hardly scuffed.

[bullittwrench]

Since it's already tight enough getting in and I can still drop the RLB another hole. What about adding some LS%?

[MasterSbilt_Racer]

What compound tires were on the car? It seems to me the rears aren't loaded evenly. More evenly loaded tires on exit will make it go forward better. Or maybe the lr tire just wasn't working?

[bullittwrench]

Had AR 44's on all 4 corners. Probably should have had a 48 on the RR. Pretty much everyone else did. The tracks not very abrasive.

[bullittwrench]

Let me throw another ??? out to you guys. Could the 0 reb. on the LRR shock be shearing the LR contact patch loose? Should I have some reb. there to "cushion" the reaction a little? It's an adj. QA1. I can dial in anything from 0-4 reb.

[billetbirdcage]

If it was me, I'd increase the Left side .5 to .6 and try again. I like to keep some rebound on the LR behind shock, start with a 3 for an overall starting spot and start taking some out as the track gets slicker. However I would always keep some in it like at least a 1 1/2# to 2#.

Is this a new engine or the one you been running with the car that got totaled? Could it be the engine is too peaky?

[bullittwrench]

Same engine and yes it's violent. We're going to live with it for the rest of the year and look at a cam change over the winter.

[billetbirdcage]

If the motor is fairly violent, you might have a hard time fixing this problem. I guess that depends on your meaning of the term violent. Can you hear the motor sound flat or stutter in the middle of the corner when he first picks up the gas? If a motor is peaky and the RPM's drop below this torque spike you get into the gas and hold it steady and as the RPM's increase (torque shoots up) it may blow off the tires without moving the gas pedal. This is very difficult to drive with the engine this way, however sometimes putting more gear in it so the RPM's don't fall below this spike helps but don't blow the engine up from excessive RPM's! Or you can try a smaller carb to increase the torque at the lower RPM's to the spike isn;t as bad and may make it more driviable.

If you can hear that stutter/flat sound in the middle upon inital throttle, you may have your work cut out for you. However this may all be wrong as you guys seemed to run OK with the older car, right?

[bullittwrench]

With this new set of heads, we've only been wicked fast when there was bite in the track. This is with either car. I think I'll bump the LS to 55% and let some rebound in the LRR shock this week and maybe drop the LLB 1 more hole depending on track conditions. Sound about right?

[billetbirdcage]

So the engine got new heads and has only been run in this new car???

If so, I would look at doing something to the engine first and quickly before you pull your hair out trying to fix an engine problem by adjusting on the chassis. If you don't fix the engine (and it is the problem) you will have spend the rest of the season trying to fix something that once you get fixed isn't going to help you once the engine is fixed. You will have to totally relearn the car with a properly working engine.

I can't say if the engine is the problem or not but it sound like it could be. It could be the car, you will have to decide if the engine is really that bad and the culprit.

If you don't here the engine stuttering at the lower RPM's you might be able to remove some iginition timing to tame it down, but that can cause out problems like high EGT temps and the like. You might talk to bill and see what he thinks.

[bullittwrench]

We ran these new heads 4 shows with the old car but never really got enough feature laps to tell anything due to crashes, mech. problems. I talked to the engine builder and he also said that pulling gear out will make it worse. These heads are just newer versions of last years. The dyno sheets are very similar according to him. We gained a few HP but lost some torque when we went to the newer heads.
Going back to the setup, what's your opinion on either:
1) Pulling the 5th coil back to 35"
2) Letting it at 37" but changing to a 350
I'm thinking 3" travel is just marginally enough. Which would be "tighter" off, a 375@35" or a 350@37"? For more instant drive, don't you pull it back?

Thanks

[MasterSbilt_Racer]

You pull it back for more instant drive. Pulling it back will also make the whole rear start to rise. This is something you may not really notice unless you get to about 33" or less.

I think that 3" is about perfect, but some people do like to see more travel. If the car is spinning at exit, I would move it back. If it is spinning some place past exit, I would try softening the spring. I bet the engine is the real problem though.

I'm curious to see Billet's thoughts.

[bullittwrench]

Mastersbilt Racer, the car is spinning at exit. I also need to add that he's getting pretty good at this trail braking thing. When he's on the curb most laps the car never drops at all. I stand between 3 and 4 right along the inside rail so I get a good view. I'm not sure I understand what you mean by the engine stuttering at low rpm. Are you talking about mid-turn? We run borla's so it's hard to hear it but I've never heard it stutter or hesitate. I don't think we're dropping that much rpm, this place is pretty fast around the top.

[billetbirdcage]

The stutter I'm refering to is a missing, lugging, or loading up of the engine midcorner when you first get into the throttle. This just means you drive into the corner say 1/4 throttle (trail braking) and when you pick up the gas to say 5/8 throttle the engine stutters or sounds like it is loaded up (too rich or carb flooding over from too high fuel pressure or floats to high) so 5/8 throttle is correct to not spin the tires but as you hold the throttle still (5/8) the engine cleans out or gains some RPM (from the car acellerating) and the engine gains a large amount of torque and spins the tires even though you didn't push on the gas harder. This just means that once the engine cleans out or gains a couple hundred RPM the 5/8 throttle is too much power and spins the tires, you didn't increase the throttle still 5/8 put the increase in power output is like going to 7/8 throttle.

I have been there and done that when I first went from a LLM to an open car, brought both car to a practice session and couldn't hook up the LM. Open tires verses specs, 2300# vs 2488# and 250 more HP and the LLM was .3 faster then the LM. I thought the car was a piece of junk everything I did didn't seem to help. A couple weeks later I had another (I have only 2 years in a LLM of total circle track experience) driver get into the car and drive it. He said "ya the motors alittle peaky and hard to drive". However when he was making laps in it, I heard the engine stubbling upon intial throttle up in the middle which I couldn't here when I was driving the car. I was plain as day being outside the car, however there wasn't any other cars on the track at h time which helped to hear it.

The engine didn't have enough compression for the cam and the carb was a little on the big side. This made the engine sluggish at around 4000 to 4500 RPM but once it got over that it took off and ran well. So I installed a smaller carb, leaned it down, and but some more gear into it to keep the RPM from falling below the 4500 RPM. This help alot but you couldn't keep the RPM above this point on some tracks without excessive RPMs at the big end. On this track the RPM actuall came down with more gear (by the tell-tac) because I wasn't spinning the hell out of the tires off the corner. You had more power and torque with more gear but you could at least control it much better.

I changed the cam and upped the compression and some other changes and the car (with no changes to the chassis) went from a car that couldn't make the field on a slick track to running around the top 5.

This whole engine deal could be way off base, but I have been there and seen it many a times if it is a home built or professional builder without alot of circle track experience. Drag racer engine builders are the worst, they make good power but reliabilty and driviablity usual stink.

#375 at 37" could be a little stiff, If you going to make a change go more then 25#. If you wish to drop the rate I'd go aleast to a 325 or 300 and see if it helps. Spring rate is dependant on the driver some like soft and some stiff. For me softening it always takes instant traction out of the car but others will tell you different, so it depends on the driver.

Moving it back may help with the instant traction but usually (for me) unhooks the car later out of the corner. Again you get guys on both sides of the fence on this one. So if you going to change move it back a fair amount and to see if there is really much of a change.

I have never like a torque arm that far forward, it always seens to slide the front end when we get that far forward. Maybe it is just the set-ups I do with my guys, but mostly we ae in the 32 to 36 range and the 36 is on the rare side. Being we are farther back means we are usually more on the stiff side on the spring 350ish.

In short try one of two things:

Leave at 37" but soften to 325 or 300 (I'd lean to the 300)
Move back to 33" and leave spring alone

Since he getting good at trail braking and if car is staying up the whole time and is against the stop coming off. If you lower the LR upper one hole this will likely tighten up the car by removing rollsteer. It will likely still get all the way up but just have less steer. That sounds backwards but if the car is lifting 5" (wedge) and it rollsteering 4" by lowering the upper bar the car will still lift until it hits the stop (5") but will have less steer (3.5"). Hope that makes sense.

[bullittwrench]

Yep, makes sense. But now i'm really unsure what I want to change. I'm going to bump the LS% to 54.8 but other than that i'm going to let the heat race setup alone because he liked it and it was fast. I like the idea of letting the 5th coil @37" and softening it for the feature. If the engine is "peaky", a softer spring should be more "forgiving".
I understand putting the LUB down 1 to lessen roll steer since the car is never leaving the bars. That would put all the bars where I run them in the heat. I'm not sure i've ever heard of a bar car going from bite in the heat to dry slick in the feature without moving a bar. LOL I'm going to let the LRR shock at a 4/3 for the heat and feature also.
Assuming track conditions are comparable to last week??????

[billetbirdcage]

So your raising the LRU to the top hole when it slicks off? Raising the LRU bar is adding rollsteer along with the added drive angle but it likely doesn't need the extra drive angle to get the car up so you are really just adding steer. While this may help with the instant traction when you first step on the gas it will (in this situation) usually just loosen the car off the corner. Usually the more a guy trail brakes the less sensitive he is to this instant traction in the middle.

Instead of raising the LRU, lower the LRL bar after the heat: this will remove steer and increase index which softens the exffective LR spring rate.

I'm not familar enough with the holes on a 07 masters to know what angles the bars are at in those holes. But if the top hole is more then 23 degrees I'd say that is the likely culpruit along with the engine maybe not helping matters.

Either that or don't do anything at all and see if the car is better in the slick with out the LRU up a hole from the heat.

[bullittwrench]

That's what I was thinking, let the LUB alone after the heat (down1) and lower the LLB 1 hole. That would put the LLB at just a tic above level for the feature. I think the LUB in the top hole is like 25 or 26deg.

[bullittwrench]

Track was black dry slick last night. Did not take rubber though. I upped the LS from 54 to 54.5% other than that used the same setup in the heat as last week. He said the car was a tic looser in(but still tight) but was almost too throttle tight up off the corner.(finished 2nd) From heat to feature: dropped LLB 1 hole, put a 350 on the 5th arm left it at 37", Upped LRF shock to 250psi. He said the car was awesome in the feature. Tight in with trail brake and great forward bite. Unfortunately though running 5th, 3rd and 4th tangled in lapped traffic causing a massive melee that blocked the track. He slid broadside into it and totalled the right side of the car. Frame is ok. Lot of body work to do, spindle, LC arm, ball joints etc. You guys know how it goes.
I asked him what we needed to do to get faster.(winner was quicker than we were) He said now he needs more instant traction in the center of the corner. 5th coil now is a 350@37". It had 3" travel in the feature. Just move it back to 35" and let it alone, or move it back and put the 375 back on?
A big Thank You to everyone who has helped me. It's tough to accumulate knowledge running 1 night a week. You guys experience has saved me many lost nights of experimenting. I do appreciate it!

[billetbirdcage]

You'll have to experiment with the torque arm spring and length to get a true answer for your driver and set-up. Everyone seems to be different on how sensitive they are to the instant traction on the spring and the overall traction on the length. This just means some people can change the spring and see a big difference in the instant traction upon inital throttle while others can't tell any difference at all. So there really isn't a right or worng answer just depends on the driver.

With that said, I do see trends with driving styles and this is my guess to how your driver will precieve the changes:

I think he will like a heavier spring, as you go softer I think he will feel a loss of traction. However too heavy of a spring can sometimes cause a problem if you are running on a track that has traction spots and slick spots, like running with the left tires in the traction on the bottom and then having to drive across the slick as you exit the corner and drift out to the wall. I also believe he will like the torque arm back some when there is traction (heat).

I take it you didn't mess with the rebound on the LR?

[bullittwrench]

That is correct. The shock is a 4/3 at 5 clicks off full reb., so I set it at 6 clicks at the shop and left it alone all night. It has 21 clicks from 0-5 on reb., so I was slightly less than 3 on reb. It's a QA1 68 series reb. adj. twin tube
If I move the 5th coil back to 35" in the feature to get more instant traction should I let the 350 on it or put the 375 back on. Had 3" travel on sat. night with a 350@37".

[MasterSbilt_Racer]

Like Billet said, you will probably need to experiment some. I'd save myself some extra work and just move it back first. Then maybe change the spring and see which is better.

[bullittwrench]

Mastersbilt Racer,
The crash put a slight kink in the diagonal bar that the bottom of the dry sump tank mounts are welded to. Should I be concerned about this? Frame rail is ok and nothing else seems hurt. That bar is in there to control flex, isn't it?


Thanks

[MasterSbilt_Racer]

That bar gives it some extra stiffness, yes. Without seeing it, I probably wouldn't worry. Just out of curiosity, is this a round or square rail?

[bullittwrench]

square rail car. If you lay a straight edge on that bar, it's kinked in about 3/8 inch.

[billetbirdcage]

I was should if you even added rebound from the inital set-up, so you when from a 4-0 to something like a 4/3.25 if you where at 6 clicks. That could very well be the loss of instant traction the driver is looking for, he may be so used to having no rebound on the LR that adding some may take away that feeling he is used to.

The reason I don't like "NO" rebound is sometimes the car can jump up so quickly that is can actually induce a loosening effect in the middle. This is really different then the way it sounds, the car jumps up very, very quickly and pivots and gives the feeling of being loose in the middle or helping the car turn in the middle. However this is usually more noticable on a tight cornered track where the driver is diamonding the track. So I like to keep some rebound in the car if possible but there are times where I would get faily low, but I haven't ever went to zero.

I think you will see more difference in instant traction out of the spring then you will on shortening it. That is an guess on my part but I'm basing that off of what the track is like and what I percieve he driving style to be. I usually don;t ever get the arm out that far as we usually loose the front end on exit when we do, since you don't seem to have that problem I'd be more inclined to leave it out there at 37". However like I said you will need to experiment some here to find what works best for you. Most guys that trail brake and enter to corner on the bars don't seem to notice much difference in how quick the traction comes in from the length of the torque arm, "Overall Traction": Yes -- "Instant traction" : not usually.

In short I'd be inclined to stay at the 37" with the 375# spring but again a guess. If you do decide to move it back (which stiffens the spring also) I'd try just moving it back as changing 25# is likely more then the slight change in rate would be from moving it back.