jon8rfc

iTrader: (1)

I have a long video I took with my phone (13 minutes, I think) of what my "cold" starts are like here in Texas. It will act find after reaching operating temperature, but even at operating temp, it still needs to be driven to cruise smoothly. Once it's warm, it can restart and idles like a champ. Smoother idle than many other cars I've been in with factory ECUs.

• The cold start will have the motor rev up high, then die. The only way to functionally start the car and keep it running is to hold the pedal for at least a good 20 seconds until it can manage on its own. It has a very annoying puttering sound during the whole warm up period that can violently shake the car when the putters are big ones. Could this be a misfire? I'm not sure if I'm running 7s and 9s or 9s all around since I've had the car just over a week.
  
• The cruising, at speeds under about 45mph, are unsteady until I've driven for many minutes, even when waiting for warm up to 84-85c. It does a very subtle lunge, as if it can't decide if I want to accelerate or not, so it's anticipating acceleration and then changing its mind. Make any sense? My passenger didn't notice it, but I feel it nearly every time after a cold start warm up until I've driven a little while. Is carbon needing to be burned off or something?
  
• Occasionally, it feels like the engine performs much more slowly under acceleration than it should. Sometimes the tires spin in second gear when the second turbo kicks in, and sometimes the tires won't even spin in first gear. It doesn't feel horribly slow, but it's noticeably slower and doesn't throw me back in the seat. I thought I noticed a correlation between the air temperature sensor and acceleration, but once I paid specific attention to that, I began to notice that it wasn't the cause as far as I could tell.

I read that it could be starved of air on startup and run extremely rich, so making the video I raised the hood and took off the plastic box connecting the intake to the IC duct and it still started up with problems. Could disabling the double throttle butterfly valves be a cure for all of my problems? I didn't find any threads in search about the dying startup, accompanied by my other two issues and solving it by disabling the double throttle.

The occasional sluggishness upon acceleration can't be a vacuum leak, right? Wouldn't it leak all the time instead of pulling incredibly strong sometimes, and other times not? It's a hit or miss it seems...double throttle? I can't pay attention to my PowerFC at all, because I have no straight highway room without cars to pull in 3rd or 4th safely and keep an eye...and I never know if the tires will kick loose and I need to watch where I'm going and take control. Passengers weigh me down and the tires almost never spin with a passenger, so I won't know if it's performing sluggishly or not since my baseline is driving solo, and since it's a hit or miss it could perform fine for many hours

On a side note, which may or may not be related--my mpg seems awful. I drove from Dallas to San Antonio on one tank of gas and had about 1/8-1/4 tank left over--this was from 10:30pm to 3am, but does that slightly cooler air make that enormous of a difference for anyone else? Once I put in my first tank of gas, my mileage went way down, and unfortunately my odometer is non-functional so I can't give accurate estimates. However, I can estimate based on my trips that I get about 40-50 miles (maximum) per quarter-tank, combined city/highway driving. Does city driving with traffic lights (not in heavy traffic) cause anybody else to get unbelievably horrible mileage? My buddies' Yukon (not the cylinder shut-down version) and Tundra don't get anywhere near this bad of mileage in the city, and they probably have worn out plugs, wires, caps/rotors, o2 sensors, etc, yet my stuff is new!

What could have gone sour from my trip on I35 Dallas>San Antonio, to now driving around town once I put in my first two tanks of gas? Is there something embarrassingly obvious that I should be doing at each fill-up? Would not putting 2cycle oil into my tank cause such a horrible dip in mpg? I asked RP about Protek-R and they were indifferent, but didn't say that I should be pre-mixing and they would have told me if they did that when tuning my car on the Dyno, so I'm not sure what changed...unless this, too, is related to the double throttle? If the o2 sensor was old, I don't think it would have worked well across Texas and then gone way down hill, seemingly instantly.

Motor was rebuilt by Rotary Performance with about 700miles on it.
downpipe, high flow cat, cat-back exhaust, RP performance fuel pump, Fluidyne radiator, aluminum AST, PowerFC tuned by RP, rats nest replaced with silicone at rebuild, IC piping couplers replaced with silicone at rebuild, damper and injectors inspected at rebuild.


Here's the long video I took (didn't want to toss it on youtube and lose the minimal quality I already had), which is 183 megs, so grab a Snickers and right-click "save-as":
http://tsccpetition.com/snoopy/rx7/V...718_135317.3gp
(if you have sound but no video, you're missing a codec, though I don't know which...I have this pack to play all types of videos: K-Lite Mega Codec Pack

I can try and do some troubleshooting, but no driving out on the road because my interior is taken apart and some parts hanging. I figured that since it was running sub-par, I may as well pull out my cluster to attempt the odometer repair or ship it off, swap out the busted Bose tape/cd deck, and order/install a steering column gauge pod and boost gauge.

arghx

iTrader: (3)

First off, you are more sensitive to small driveability quirks and inconsistencies than most people who own modified 17 year old sports cars. You remind me of myself a little bit in the sense that you really like how consistent "normal" cars behave and you want that out of your Rx-7.

I've seen the video but I don't have the car in front of me. For discussion's sake (you did take it to a reputable shop) let's say there isn't a major mechanical failure or incorrect work done to the car. I also don't have a copy of your PFC map nor do I have useable logs of these problems occurring.

I can already tell you that it is most likely a tuning issue. Cold start is time consuming to tune. Basically you get the car to idle and drive pretty good when it's warm first. Then to tune cold starts you start it up, make some adjustments to see if it helps. If you don't get everything dialed in you have to let the car sit overnight before you can mess with it again. You can get it "good enough" in one, maybe two sessions of this.

To get it just right (drive very close to stock despite changes in weather) you have to do this process over and over again for up to a year as the season's change. The PFC is not a learning ECU like what comes factory on newer cars.

If the throttlebody is adjusted correctly it may not be getting enough fuel. I've seen this before, it's often the water temp warmup enrichment table that can improve/solve this (adjustable in the Commander).

Another common one. A lot of times the timing needs to be retarded. There is a warm up ignition retard setting in the PFC. A lot of tuners disable this for various reasons, but without careful tuning of the leading and trailing maps you can have significant popping/puttering during warmup. This is another one that's tedious to tune. Retarding the timing and getting the AFR correct can significantly reduce or even eliminate this problem. In the video it sounds exactly like one FD I was working on. Retarding the timing by about 7 degrees significantly reduced the popping sounds.

Yes, it drives worse when it's cold (or is this studdering happening when fully warm as well?). That's occurs often enough on a PFC. It can be improved upon, but although not necessarily eliminated. The PFC does not have a gazillion tables to adjust fuel, timing, and idle during warmup like some other computers do (AEM EMS). And even if it did, it still takes a long time to get that set right so it drives as good as stock.

It could simply be that the engine makes less power and torque as intake temperatures increase, even though everything is still set up in the PFC decently enough. I don't have your map and I don't have any good logs.

The double throttle system has been on fuel injected rotaries since the 12A Turbo in 1983. Yes it's another system to complicate things (Rx-8's drive-by-wire finally eliminated it), but unless they are stuck closed due to a vacuum routing mistake then they aren't going to cause a problem on a manual transmission car.

Still sounds like a tuning issue (tip-in fuel). These little stumbles and hesitations can be very time consuming to tune out. It's the nature of a modifed car I'm afraid.

Sounds like a tuning issue again. Tuning highway cruising can also be time consuming. It depends what they did with the airpump on the car, the fuel maps inside the pfc, and the o2 feedback setting. I can't tell you much more without datalogs.

You can't easily tune cruising fuel without an on-board wideband and road tuning, or a lot of time spent on a loading dyno. And time is money.

There's not enough information, but I highly doubt premixing will do anything noticeable.

Motor was rebuilt by Rotary Performance with about 700miles on it.
downpipe, high flow cat, cat-back exhaust, RP performance fuel pump, Fluidyne radiator, aluminum AST, PowerFC tuned by RP, rats nest replaced with silicone at rebuild, IC piping couplers replaced with silicone at rebuild, damper and injectors inspected at rebuild.

I saw it. I've seen all that many times. It needs more tuning, and that kind of tuning takes time. You'd be surprised how many people don't care very much about the symptoms you are describing. Lots of people don't mind keeping their foot on the gas for 30 seconds. Lots of people aren't particularly bothered about a popping sound during warmup. Lots of people will tolerate a small hesitation as they lay into the throttle, as long as the car still hauls ***.


Here's my advice. I guess it's possible that something could have failed mechanically or electrically somehow (what do I know, I'm nowhere near the car). The most likely scenario is that RP built your engine correctly and didn't make any real mistake. They put it on a dyno and tuned it enough so that it hopefully won't blow up. All the other little things that bother you can take a lot of time to get just right. And time is money. That's the nature of running an aftermarket computer, especially on a system that does not use a MAF sensor.

You can take the car back to RP and they should be able to improve the tune. But if you want to get rid of all those little quirks and inconsistencies with the weather, tune the car yourself. Nobody else will be able to put the time into it to get it up to your standards. Check out my thread which has an introduction to PFC tuning: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-make-your-untuned-pfc-basemap-safer-idle-better-no-datalogit-needed-841706/ also buy a Datalogit box and PM Chuck Westbrook (cewrx7r1) so he can point you in the right direction with his Datalogit tuning notes.

jon8rfc

iTrader: (1)

Thanks, it's a nice relief that it's typical to need additional tuning rather than "I've never heard of that and it could be countless things". I'll give another run through the PFC manual and check your thread, which looks like I should be able to put my OCD to use on the startup idle and get some promising results! Hopefully, I can find a nice deal on a Datalogit, because I didn't already budget that in for this month with my other fixes/add-ons I want to complete by August 16. Thanks again!

willjs7

iTrader: (1)

tune the nos timing and you will run 9's


good luck man, defiantly sounds like a tune issue to me, make sure you use fresh plugs when doing all of this!