Leon

I was on vacation for a few days and decided to take a look through Milliken & Milliken to see what they say about Ackermann as it pertains to this discussion. Here is a direct quote from the Milliken book. Milliken & Milliken, RCVD, p. 713-715 in Ackermann Steering Geometry, section 19.2. Some words are bold in the book and others I made bold for emphasis. The Millikens' perspective echoes exactly what I've been trying to explain. As the Millikens point out, when you're racing the turns are relatively large radius, thus Ackermann effects are minimized. Here is where your static alignment settings come into play. What does this mean and how does it tie back into our toe settings? The Z has parallel steer, meaning that if you draw a line along the longitudinal center-line of the tires while they are steering, those lines will never intersect (theoretically). In other words, the relative angle between the wheels does not change as you turn the steering wheel. When you make static toe changes you are changing the relative angle between the steered wheels. For example, let's say we set the front wheels with static toe-out. We are on a road course, so it's safe to assume large radius turns. Now when you turn the steering wheel, the inside wheel will always be at a higher steering angle than the outside wheel, meaning that the inside slip angle is going to be higher than the outside slip angle (unless the car tears in half). Think of this as psuedo-Ackermann steering. This is the opposite of what we want in a high speed corner. In reality, whether you're on a road course or an autoX run, there's more to handling than steady-state corners. I am not saying that certain, or any, suspension settings are always good or always bad. What I am saying, and have been trying to explain, is that setting static toe-out will decrease the capability of the front of the car to generate lateral force (in steady corners) because of the aforementioned phenomena, and thus introduce more understeer than with static toe at zero or slight toe-in. To sum this up, this is a discussion purely about understanding the effects of steering geometry and toe-changes on handling. A properly set up suspension will factor in all facets of wheel alignment (toe, camber, caster) and suspension geometry (camber curves, bump steer, ad nauseum) along with the desired needs from the vehicle in order to get satisfactory performance. However, a more informed person will be better and quicker at making the right decisions.

I can't do that, at least not now. I'd need consent from some people. Well, Laguna is less than 2 hours from me. I'm sure I'll be doing track days there when my Z is finally sorted.

Let me sum my answer up for this one. Clearly, the inside tire can have toe in or out relative to the outside tire, that's what this whole discussion is about. However, you don't seem to understand what independent means, maybe this is a semantic issue. Yes, the wheels each have individual slip angles that may or may not be equal. Notice I used individual and not independent, those are two completely different things. The slip angles are dependent on one another because the left and right wheels are connected by links. I can write you an equation that relates left slip angle to right in a certain situation, e.g. given velocity and turn radius. What does that mean? It means that one is dependent on the other. Here's an example, say your car goes around the same exact corner, at the same exact speed, with the wheels traveling over exactly the same spots over and over. Given the slip angle that is produced on the outside wheel, is the inside wheel going to have different slip angles every time (or anytime?). Can you do anything, given these parameters, to change the inside tire's slip angle without changing the outside tire? The answer is no to both, and that means they're dependent. I think we should have that out of the way now. I'm curious if you have any response on the more pertinent parts of your argument?

But the two wheels are solidly connected, how in any way can the slip angle of the two front wheels be independent as you imply? I completely understand that each tire's slip angle is defined by the difference between wheel centerline and actual path, but that in no way means that the slip angles left to right are independent. There could be myriad reasons why nobody runs that, such as it compromises other aspects of handling (which any suspension setup does). I am not arguing this, what I've been trying to get through to you is that the ideal toe angles in high speed corners are counter to what most people believe. I think I've gotten you to understand this, maybe somewhat. That would be cool, and wouldn't you know it, I have done a bunch of research and a paper on the topic. This portion of your argument is invalid for a reason that I already mentioned. The definition of perfect Ackerman steering is when your wheels follow a path that produces no tire scrub, with neglected lateral forces and slip angles. It's purely, solely geometric steering. Imagine solidly connecting two bicycles and finding the individual steering angles that create no scrub at low speed. These angles are going to be different, even on the same corner when you increase velocity. All this stuff about Ackerman steering is valid for low speed turning. It is a very typical mistake of assuming "Ackerman steering" (not Ackerman steering angle) has anything to do with high speed driving. Now you are correct that different corners need different toe angles because lateral acceleration (a=v2/r) is different, therefore lateral force is different, ergo load transfer is different. Yes, it works on the super speedway, but how about a long sweeper or a high speed kink, etcetera? Everything is a trade-off, it's up to the user to decide what is best for each sitation. I'm just providing the facts. No problem, I'll report the results if I'm able to make up a proper, valid test for it. Again, suspension setup is a series of compromises involving multiple variables, as other posters have alluded to. What will work for one track will not work for another, let alone one corner to another. Take my information for what it's worth, a small explanation of vehicle dynamics so that hopefully someone can take advantage of the knowledge and have a better understanding of what they're doing. I hate relying just on anecdotal evidence espectially the stuff that's been through many mediums. It becomes a game of broken telephone (or whatever you call it) where information is taken to be gospel without actually asking the last guy what the heck he's talking about. It happens all the time, and the guys that have been "around it for 60 years," while usually full of good advice, tend to be the worst at spreading false truths as well since they are never questioned on the reasons behind their statements. FWIW, Leon

Thanks BJ, I got tired of repeating myself. I also agree that there are plenty of things to play with with regards to suspension setup, but ideal slip angles are what you are ultimately trying to achieve with a given setup. JM, how can you say that the ideal slip angle wont create more lateral force? That is the whole point of optimizing slip angle!

Alright JM, believe what you want to believe, I'll talk to my F1 guy and see what he thinks. I'm sure he'll have some good insight. Cameron, I think you have a decent idea of what's going on. I'm not sure if the Benetton cars were running bias, but he was there around '00-'01 or so, I don't remember exactly.

I understand this may be "mind blowing" but yes it does make sense to turn the inside tire less once you realize the physics involved. You are still thinking completely geometrically and not considering slip angles at all and how they pertain to vehicle dynamics. You are either not listening to what I'm saying or you don't understand the concept of slip angles. Slip angles dictate the relationship between the tire and the road when cornering at high speeds. Stop thinking about where the centerline of the tire points and start thinking in terms of what are the optimal slip angles given a normal load and lateral acceleration. Look at the Milliken figure I linked earlier and the answer will be staring right at you. A less loaded tire needs less slip angle to generate its maximum lateral force, therefore you want the inside tire at a smaller slip angle than the outside. It's simple, but you have to understand slip angles first and I'm not convinced you do judging from this discussion.

I'll add that it doesn't make sense to turn the less-loaded tire more. A less-loaded tire will perform optimally with less slip angle than the higher-loaded tire at the front wheels, and front slip angle is driven by steering angle. With toe-out, the wheels are inherently in the wrong position for this. Therein lies the core of this argument. Here is a reference photo from Milliken & Milliken: http://features.evolutionm.net/imageview.php?image=1538

JM, I honestly don't have the energy for a long discussion after 12 hours of work. I will say that you are not considering (understanding?) slip angles in this discussion at all, and those are very important pieces to the puzzle. FWIW, I have had long discussions with a former Gurney's Eagles and Benneton-Renault F1 engineer and he would tend to agree with me, at least in a general sense. I don't have the experience of playing with Z-car geometry, but there are physical laws that govern vehicle dynamics which come into play no matter what vehicle you're driving. I just don't feel like dissecting your long, largely unspaced post right now.

Jon, I'm not sure if you're arguing here or what you're trying to say, so sorry if misinterpreted your post. I'll point out once again that static toe-out induces steady state understeer. You're right about the inside tire being less loaded during a turn but its effect is still prominent enough, and if you're looking to squeeze out all of the car's cornering capability, you want the inside wheel toed-in relative to the outside. The outside wheel has a larger effect, and since it was statically toed-out, when loaded it will be at a disadvantageous slip angle when compared to zero toe. Yes, static toe-out will quicken the transient turn-in, but if your car is stiffly sprung (Cameron's car) then weight transfer will happen quicker. It's all about compromises, are you willing to compromise steady state cornering prowess for quick turn in? Maybe for autocross, but definitely not for road racing. Cameron speaks of lap times, so I'm trying to discuss what is pertinent to his situation. Let's also discuss Ackerman steering. Ackerman steering is only advantageous in low speed turning, with no weight transfer and no slip angles, i.e. a parking lot. It tries to accomplish the perfect geometric turn, with no tire scrub. During high speed cornering with weight transfer and high slip angles, you're in a completely different ballgame, so to say. I don't want to be argumentative, I just want to provide helpful information to the discussion.

The pictures of the ID plates don't match, they're from different cars. As Owen pointed out, build month/year are on the door jamb plate.

I guess I mixed up camber angle and slip angle in my head.

Like I explained in the prior post, running toe-out up front will tend to understeer when in steady-state cornering, with the positive being that it makes turn-in a little quicker before much weight transfer happens. Before turn-in, the inside wheel already has a slip angle before you even turn the wheel so you produce lateral force quicker initially. However, after weight transfers and you reach steady state, the outside tire is loaded much more than the inside. Thus, your outside tire is producing the majority of the lateral force when compared to the inside. With static toe-out, the outside tire will need to be turned more than if you have zero static toe, or "understeer." In high-speed corners, you want the inside tire toed-in more than the outside (see "reverse Ackerman") since the outside tire is more loaded, and thus requires a higher slip angle. In the rear, in order for the car to rotate, the slip angle points outside of the body, tending to yaw the car. With the rear tires pointed in, initially the slip angle points inside of the car. A similar effect to the front occurs, where initially the inside rear lets the car rotate. But, once you reach steady state the loaded outside wheel has a smaller slip angle than in the zero toe situation, therefore the car does not rotate as much. Therefore, both your front and rear suspensions are set up for understeer. If the rear is unsettled during braking, I would adjust f/r brake balance before fiddling with the alignment. You need much more braking up front than the rear, and this is exacerbated with higher grip (slicks) as it causes more weight transfer. You may need as much as 80-85% front brake distribution. Here is a little article I found on google, just search here and on google with keyword combos like slip angle+handling, etc. I'll also refer you to Milliken & Milliken's Vehicle Dynamics book.

If you decide to center the butterflies, just loosen the screws so you can move the butterfly. You will damage the butterfly otherwise. The butterfly adjustment tip is passed down from my conversation with Mike Pierce of Pierce Manifolds.

This sounds like either a vacuum leak or a linkage issue. Test for leaks as Matt mentioned. To check the linkage, disconnect the throttle arms and see if that changes idle speed. If not, physically close the throttle at each carb and see if that changes idle speed. If idle drops down, use a flowmeter and get readings at each carb. Individually blip each carb and again check each carb with the flowmeter. If they are flowing much higher than they did before then something is not right. The offending carb(s) may need the throttle butterfly centered properly in the throttle bore, as you said they were recently rebuilt. Once they idle properly with the linkage disconnected, reconnect and make sure there is no binding or sticking in the linkage. The carbs should flow the same whether the linkage is connected or not. This is critical to a proper triple setup.

Very nice! I've been waiting to see the M3Z get going!

I didn't have a chance to read over that full article yet, but it seems like the guy knows what he's talking about. Regarding L-series cooling, here's the sticky: http://forums.hybridz.org/index.php/topic/59029-head-cooling-on-cylinder-5-solutions/ For being a non-engineer, I think you have a good grasp on things. If you're interested, pick up a copy of Heywood's book, otherwise known as the "IC engine bible."

It may be the angle of the photo in your third post, but how close is the rear ARB to your half-shafts? I had a bunch of clunks and rattles in the rear of my 260Z so I investigated. Mine was missing a diff strap bolt and had a lonely end link on the left rear control arm with no ARB attached. WTF? I removed the end-link and the metallic clanking was gone. Then I attached the diff strap and acceleration clunk was gone. So, check the ARB and end-links as another simple thing to do before tearing things down.

I thought that bias ply tires like more camber than their radial counterparts? It also looks like you set up your front end to understeer. As the outside tire gets loaded, it wants higher and higher slip angle to generate lateral force. With toe-out, more steering input would be required to generate a certain lateral force when compared to zero toe. I believe your rear end is also set for SS understeer. Your car must push quite a bit.

I have the same exact problem on my 260Z. It is an electrical problem, not enough voltage is getting to the solenoid. Get your DVOM out and measure the voltage to the solenoid when it clicks. From my research, I believe the solenoid needs at least 9V to activate the starter. Because of old, corroded wiring connections, the voltage drop is large and the solenoid does not get the voltage it needs. Follow Mario's advice and check and clean all connections. Quick test, if you jump the solenoid, does it turn over every time?

Tony, move to Russia! http://jalopnik.com/5713727/russian-motorists-viciously-beat-drunk-driver-on-video Warning: Graphic content!

ZCar Garage is in San Jose, on Archer street close by to the airport. Rob has a really nice RB26 Z.

No doubt, an S2000 or E36 M3. One of those will be my next DD. I have driven both generations of S2ks, along with the E30 and E36 M3. The S2000 is honestly amazing, from the engine and shifter to the suspension, they all work together in perfect harmony. The E30 M3 is raw, but very satisfying to drive and corners like nothing else. The E36 M3 is more refined and torquey with those extra 2 cylinders, but still has that sports car feel. Both BMW and Honda have engineered their cars very well and everything from button positioning to the feel and sound of the door closing has been thought out. I've met Steve Dinan (founder of Dinan Engineering) and after someone else made a comment at the expense of "Honduhs" he replied that "Honda is the BMW of Japan." I seem to agree! FWIW, I'm 6'2", 190lb and fit into any of these cars without a problem, but if I was any bigger I think I'd have a tough time.

That's the intake for the air correctors. Check your float levels, I bet they're too high. I don't have my Weber book with me to see what 45DCOE float height should be. Float specs vary depending on carb model. What does the top of your carb say, is it 45DCOE9 or another model? Setting the floats correctly is essential for proper carb operation. If you are interested in tuning triples and how they work, I recommend getting Braden's book. It's a great resource to have on hand and the price is nothing to complain about! Otherwise, both this site and google have tons of info. Hey, there's even a sticky!

Ok... Maybe as a baseline, but not a final design. You need to design the collectors for resonance at your design rpm with your valve timing. The pipe must be big enough as to not rob horsepower. You can't just make a blanket statement like that and expect everything to be sized perfectly.