Afshin

I agree that loosening the sway bar is a better aproach than lowering tire pressure which is why I will do that first and then try playing with the air pressure. I just wanted to clarify that lowering front tire pressure would not worsen my oversteer as was stated earlier. I fully agree that it may or may not help (need to start somewhere). You bring up a very valid point about using a pyrometer to fine tune the suspension since knowing which tires and what section of the tire is heating more or less... can provide all the info one needs to fine tune the suspension correctly. Unfortunately I don't have one, and as usual I'm already overbudget. But then that never stoped me before , so does anyone know of a CHEAP (less than $100) pyrometer that works ? (I don't need the best, just cheap and moderately accurate/sensitive) Thanks

Great, that seemed quick and painless. You're all set for the weekend now, hopefully the cops are relatively easy going in your area

The 13b-re twin turbo should be amazing in the Z, specially for road course set up and all the wonderful twisty roads in the bay area (we're neighboors). i can't wait to hear about or see the final project. I think it will be worth the effort and headaches. Nothing is like a unique set up (as long as it makes good sense such as smooth, high power,light weight and 2 wonderful turbo's).

Well I doubt that it's the timming being retarded by the cpu causing the problem. I have had 3 diiferent 83 turbo set ups with factory system over theyears, and none of them could retard the timing that significantly when overboosted and knocking. In other words the ability of the factory CPU to retard timimg enough to avoid knocking/overboost is very very very limited. It would be nice to know what the boost is. fuel delivery is definitely a possibility as already suggested and other consideration would be leaking WG actuator and boost leak see "can't hold boost" post on this forum (James "spork" has a nice write up on checking for leaks). BTW did you do anything else at all when changing from the 81 to 83 CPU ? The 83 cpu could be faulty, but that is not so common, perhaps you could put back the 81 cpu on and see if the problem goes away, then you know it's not fuel or leak related.

Hi Guy I got the Konig Imagines and I absolutely LOVE the way the look on the car (nice red new paint, similar to Cody's 8) ). I also put in the black and red aerospeed seats and an isotta steering wheel which look perfect in the car. I will try to get some pictures up soon. DO you have pics with the Konig Monsoon Rims (i looked at your web site) fully mounted?

I agree with James (nice write up) that you may likely have a leak. I would also strongly consider shortening the WG actuator(even though it is tight) since it's a relatively common problem. I just redrilled a hole next to where the pin goes and effectively shortened the rod without any cutting. I really don't think that you exhaust is the restriction and would not mess around with that for now. COnsidering that your turbo is able to quickly build the 12 PSI boost, I think it is less likely that the turbo is the major problem. You build boost then lose it. this suggests WG failure or leak more so than a restriction or turbo failure. Another possibility is improper fuel delivery. I know you have remapped, can you calso check if fuel mixture (and timing)is correct at peak boost? Good luck and keep us posted.

thanks for the link Carl. nice summary. I also did some more homework by reading the section on oversteer in Bob Alexandre book "performance handling". According to him and the web site link lowering the front tire pressure as I thought could definitely help and not worsen the oversteer. At this point I think I will loosen the rear sway bar first and give her a run, then I will give it a second run with lowering the front tire pressure a tad. I will post an update after I get the chance to take her back into the twisties

Dan, I know that under static condition (no cornering load) decreasing tire presure increase contact patch size, however I thought that a underinflated tire under load when cornering would role more and provide less pressure in the middle and inner side of the tire (eg low pressure tire wear more on the side and less in the middle).. which in effect would reduce the effective contact patch. If I remember correctly there is only about a 3-4 psi range for maximal tire grip/effective contact patch. So if one where to either overinflate or underinflate the tire grip would be reduced. If effective tire patch size was to increase with lower pressure, then lower pressure would result in better handling and grip which is not the case . In other words this is how I thought it thru : less pressure=softer tire sidewall = more tire roll = less effective contact patch = less grip. (=better handling balance) Do you agree?

thanks for all the input. In terms of tires I am running Kumho 712 which are relatively new (about 3000 miles) and are strong peformers. to date the tire wear is even. the car was aligned a year ago and the rear toe was within specs (but under no load off course) I can't remember the camber but it did not raise any alarms at the time and my tire wear remains even. My understanding was if the rear tire pressure is optimal, then having slightly low pressure in the front will decrease the effective front contact patch size under load reducing grip and hence in this scenario getting the car closer to neutral handling. Am i missing something? Also has anyone played around with the rear camber and have any suggestions for a range to set when I get the new bushings and allignment?

My current set up includes a 1983 280zx turbo with eibach’s, tokico’s (nonadjustable), 17†wheels with 225/45/17 Z summer tires and new urethane sway bar bushings. Car handles quite well except for a steady oversteer which seems to limit my cornering ability prematurely. The car clearly handles much much better than stock, but it feels like the oversteer is less predictably than before and is a little more difficult to straighten out with the accelerator once I have exceeded the limit (which is quite often ). My goal is to maximize handling for serious twisties and mountain roads, which in this case is to minimize the inherent oversteer in the car. I would greatly appreciate others input/experience with the ZX suspension set up I am considering these options: -Loosen rear sway bar (since stiffening front would require new larger bar) -Have front tire pressure slightly lower than rear -New control arm bushings. I expect that my current bushings deform under load resulting in rear toe (and camber) changes. Before I get new bushings, does anyone have any experience with the motorsport bushings that allow for camber change? And if so has anyone found the amount of negative camber that can be dialed in without causing too much premature tire wear (some is OK) ? I would greatly appreciate all input regarding decreasing the amount of oversteer. Thanks.

Yes the eibach's are progressive rate, I know you can easilly get them for at least $229 from Adam at http://www.z1auto.com. You can do a search a see if anyone else has a better price or not. I had the eibach's on a 77280z with a zx turbo transplant a while back, on a 1990 supra turbo and my current 280zx turbo. I also just put some myself on my friends 1994 prelude and 97 Maxima. The experience has consistently been great. One minor complaint was that the suspension travel was a little low on the 280z with the eibach's so it would bottom out easilly on potholes. However, in all applications the ride remained more comfortable than we expected (progressive springs do really work). The only time that I was not satisfied was when I used Suspension Techniques on a different 280zx turbo, the handling was great (perhaps even a little better than the eibach's), but just too stiff for a daily driver in my taste (I must be getting old). Unless you have lots of rough roads where you drive, I would not hesitate too much about the eibach's. The other option would be to get the european spec springs from motorsports which will lower the car a tad and provide a much more reasonable compression rate than you current and likely very old/worn U.S. spec springs while maintaining a high level of comfort (in between eibach's and stock). Hopefully some other people can give you feedback about there experience with the eibach's since performance gain to comfort loss is such a subjective measure.

I understand the money being tight, however, I believe that the tokico's are significantly better than the KYB's (which I feel are marginal in performance). Considering the long term increase in driving pleasure and performance with good suspension components I would certainly pay the extra $100(it's to easy to regret it later). You could also consider getting some eibach springs for about $200. yes, yes that is even more money, but there will be no labor costs at this time point and the difference in handling and feel is phenomenal (I can't emphasize this enough). you can then do the other suspension mods at a later time since the labor will be seperate anyway(eg bushings, camber plates, adjustable tension rod...) Another important point is that If you get performance springs now or later the KYB's may not last very long and will not match the shorter and stiffer springs nearly as well (ie not enough dampening) as the tokico HP's. So it looks like you will need the Tokico's either way. Enjoy the ride

Uh, well my post exactly said the same thing "it can change the direction of load i.e. compress vs extend but not the amount or total force apllied to the roof" so I'm perplexed by your response (and I've only had one drink tonight ). Second, when upside down, as you also mentioned the load changes from compresion to tension which can be better handled by the roof. Third the car handles greater compresion and tension loads during driving over dips and bumps, racing and cornering with 2 passengers without the roof ever collapsing or tearing. The jack stand example I gave earlier is another scenario when significant load is exerted on the roof (tension or compression based on location) which again does not damage the vehicle. The whole point being that cars experience significant tension and compresion load on the roof all the time without problem, so having a stripped car on a rotisserie which would cause less load should not be a primary concern. True, the doors do add significant torsional stifness. However, a upside down car in not experincing much torsional load. I doubt that the single door latch can have much of a role in preventing the upside down chasis from flexing (that is achieved by the box sections in the chasis and the transmission tunnel wit the roof spreading/balancing the load). Perhaps i should have made it clear that I was reffering to the role of the doors on static load as applicable to this scenario as oppossed to dynamic load or torsional rigidity. I would certainly agree with you if we were talking about driving and cornering, were i would definitely recommend keeping the doors on

The actual load on the roof does not change when the car is flipped over. When the car is on the ground almost all the load is on the chasis and a small amount is on the roof which remains mostly unchanged when upside down (it can change the direction of load i.e. compress vs extend but not the amount or total force apllied to the roof). Imagine a concrete slab with a tent on top, now flip the concrete slab over, there will still be no load on the tent. For a car think of the chasis as the platform, now even though the roof does take some load unlike the tent example, the amount does not change with flipping of the car. The instance in which the load on the roof would change is when you change the location from which the chasis is being suspended. for example if you put jack stands in between the wheels (eg under the door), you flex the chasis and increase the stretch load on the roof. Conversly if you put jack stands under the bumpers (away from the wheels) you then compress the chasis and increase the compression load on the roof. Since the car can manage all off these scenarios non stripped at over 3000 lbs, you should not have to worry about it on the rotisserie and stripped. Also keeping the doors in will not help since they do not bare any chasis load (only their own weight). Now if I only had the patience to rebuild a car at that level Good luck

The problem with the RRFPR remains that the ECU is never awar of its presence and hence can't adjust for it. It will be difficult to tamper with a stock system to adjust appropriately, i.e. if you adjust the air flow meter to read less air then the car will run lean when the RRFPR is not increasing fuel pressure. if you are able to change your ecu parameters baced on variable conditions (boost,rpm, load...) then you don't need a RRFPR. The RRFPR only responds to manifold pressure, hence it can't allow for optimal fuel enrichment based on RPM along with manifol pressure. So there will be a rich mixture under boost and lower RPM (max boost can easilly be reached by 3000 rpm and in a high gear such as 4th the time from 3000 rpm to 5000 or 6000 rpm for the next shift can be significant). The varying injector duty cycle at different RPM based on the ECU results in the overal increase in fuel delivery by the RRFPR to remain as a percentage increase of the ecu program as opposed to a fix amount of extra fuel delivery. This feature makes the RRFPR tolerable when used judiciously. Also higher pressures running through the injectors are much more damaging than having a longer duty cycle(maxed out ECU) . Higher fuel pressures are clearly associated with injector failure. Additionaly low pressure is not a good way of leaning the mixture to compensate for larger injectors since it is associated with poor atomization of the fuel (poor spray) and hence inconsistent combustion. In conclusion I believe that the RRFPR can be slightly beneficial if used conservatively and damaging if relied upon. Considering the cost of the units and questionable overall gain in the big picture I would look for better solutions

I do agree with you Nathan, you are clearly correct in saying that it results in a rich mixture under boost at low RPM if it is set up to to account for lean conditions at high RPM. I had used a RRFPR for 2 years a decade and 3 turbo Z's ago and is now in my garage and not used in my current set up (hint). My point was only to clarify to everyone that it only increased fuel mixture as a percentage and not fixed amount and under high boost condition (not that you ever claimed otherwise). The reason for bringing this point up is that in the end it does not affect driveability in any noticeable way unless you rely on it exessively by grossly increasing fuel pressure. In my experience the RRFPR can serve as a effective band aid, but certainly not as the solution of choice .

Hi, my understanding is that the RRFPR will raise fuel pressure in accordance with manifold pressure (ie boost) only, so if there is low boost at 3000rpm it will mimimally affect fuel pressure/delivery, however if at 3000 rpm you are running high boost then it will richen the mixture significantly. The ECU will vary the pulse width according to air flow or mass or pressure depending on your set up. Either way the RRFPR will not add the same amount of extra fuel at 3000 rpm vs 6000 at low or high boost since the ecu will still change the injector pulse width. The net result is that it will increase fuel delivery by the same percentage under boost only. So for example at 6 psi it would increase fuel delivery by 10% over your ecu program for 3000 or 6000rpm accordingly. At 0 psi there would be no effect and at 12 psi there would be a 20% increase from baseline ecu programing for any rpm (these numbers are made up as an example only) I hope this helps