Car #: 76
Year : "You Pick" Posts: 4422
When the IAT heats, you lose power and that is normal. Have you been to the dyno to see your power drop off cold to hot, hood up and down?
Here are the most common issues I see with new folks and this topic.
Sometimes nothing is wrong, power drop off as the day/motor heats up is normal.
Morning times are faster and the motor pulls more RPM due to good air. Measure this session to session with a simple weather station. Generate a spread sheet of what to expect. Grip changes too but most of the time loss is the bad air.
Relative to the field, did others drop off as well? I like to watch three teams each weekend with the lap charts to see what they did session to session. One will find time on driving and or setup but the other two will be near the same as me. I find that most drop off. Only those who had a bad early session or really found the setup stay equal or get faster later in the day.
That brings me to this, if working on setup make damn sure you know what the expected drop off is in your car. I get calls every weekend from guys who are scratching heads having made a bunch of changes to go the same speed. The same speed in bad air is an improvement. I tell those guys, front runners, DONT TOUCH IT, call me after the morning session. They don't call but I get a text how it was faster. MASTER WHAT THE CAR DOES IN DIFFERENT AIR OR YOU WILL SECOND GUESS AND CHASE YOUR TAIL!
Racing is about baselines. Establish a baseline for everything down to tire rotation on the rim. With respect to the motor, leak down, compression, fuel psi, oil psi, water and oil temp, throttle cable tension, dyno. Then, when worried, compare and rule out items to see if anything is real or lost under the same conditions. (head gasket, hard part problems etc...)
That said, since you had power loss in session one, here is my short list assuming you have already compared the starting motor data to the after problem motor data.
(top issues from 100 cell calls past 10 years)
Did you installed new electronics? Coils etc...
What is the gap, hot, of the rear brake pads to rotor, emergency brake adjuster? (reason my cars don't have it)
Did you fish scale the car? Has the roll resistance changed suggesting front brake drag, tranny, diff, cv drag etc....
Did the drag increase hot verses cold, if so what was dragging?
Obviously you can have fuel psi issues too. Assuming you have not altered the regulator down, YET, then the pump is not tops on my list as it produces more than needed fuel with the RP. It can still be the issue but let psi data guide you. Best thing to do is to get data on all of it and analyze what might have changed. No need to buy parts until you go though the process of elimination via data. If that shows no unusual drop off, it's drag or coils.
Thanks and that helps a lot. Power definately changed relative to the other SM that was running in TTE. In the second session after I went back out to confirm something had changed he pulled me down the back straight pretty hard when before we had been very equal. I still need to pull the data out the car to check that as well.
Great point on checking the alignment and rolling resistance. Coming from a 350hp car I didn't even think of that as an impact. Silly me.
Good news on the pump. I didn't change the fuel pump or coil when I bought the car, but the wires and plugs are new.
At the very least you've given me a great start. Knew I picked this class for a reason.
This was a definate and sudden change. Good one lap bad the next so I'm sure it wasn't just the car heating up. Could certainly be alignment with those symptoms though.
Car #: 76
Year : "You Pick" Posts: 4422
Several questions on rear brakes, here is what I do.
The pads and rotors grow about 7-8ths. I start with 8 and then check play when hot.
Hot and with all metal clips removed you should be able jack up the car, move the wheel back and forth and see the pads move easily in the slop of the bracket. Remember, to lose is just a long pedal but tight can and does mean poor performance.
This is part of my pre qual and race check list.
Also, check the fronts too, have a rebuilt free caliper on hand, not uncommon to replace them to prevent drag during a weekend.
Here's a poor screenshot of the data from the lap I lost power. Both laps have the same APEX speed in tun 4, however you can see I'm 4 mph slower by turn 10. Still working on the video. Haven't had a chance to look at the car yet.
Spent a little time in the garage and ruled out a few of the simple things. I think I'm going to have to put this thing on a dyno to do further testing.
Ruled Out - No sticking brake calipers - Alignment Checks Out - No Codes - No detectable vacuum or exhaust leaks - Plug gap is good - Fuel filter is not clogged. By the way, on the fuel filter, is there any way to stop the flow of gas when you pull it out. It dumped almost 2 gallons of gas into my drain receptacle when I pulled out the filter.
I only have a simple OBDII checker at the house so I can't check the timing. When I get it to the shop and on the dyno I'll get some more data.
Hey Duncan, dumb question, but do you still have the heatshields on the exhaust manifold? I had mine off for a time this summer, and experienced something similar to you at one point. Putting the covers back on helped, but running with my lights up helped more, but that really isnt an option for you. Can you pull IAT data from your logger?
Golf tee in the fuel line has worked for me in the past. Growing an extra hand couldnt hurt either.
Now I definately need help sorting some things out. I got the car on a dyno yesterday. Here's what we found.
- Definately down on power. I posted my dyno (105hp) against a stock 99 as reference.
- Car is not running lean. A/F is right around 11.5 - 12.0 at redline. - Timing is approx 22 degrees at redline (using OBDII scanner) - Plug gap is good
- Big Thing: Turns out the car is a CA car (has a pre cat). Will be checking to see if the cat is clogged.
- No input from the VSS. Reads zero. Didn't have time to get into it on the dyno. I know it worked when the car was stock and I drove it to work, however hadn't worried about it since I was using GPS for speed on the new dash.
- Fan doesn't turn on. Verified it's not the fuse or the ground to the fan. Coolant temp sensor shows a good reading on the scanner. Need to do some more investigation.
Any Thoughts? I'll be buying a non CA manifold to try on the car. Suggestions for a good source on used parts?
quote: By the way, on the fuel filter, is there any way to stop the flow of gas when you pull it out.
I temporarily plug the fuel hose with an old bolt until I'm ready to *quickly* put the new filter on.
Personally, I would buy new exhaust from MazdaComp.
Don't use an old bolt on the '99 fuel lines. The "quick disconnect" fittings use a small gasket to seal the connection. Using a bolt would likely nick the gasket. Best method is to have as little gas in the tank as possible to prevent gravity from pushing fuel through the line. Pull the fuel pump relay and start the car, let it run until it dies to bleed off line pressure.
"Nothing can be simple. Everything's got to be a pain in the ass." - C. Adams
Coolant Fan: The coolant fan does not turn on. I've let the car get as hot as 208 degrees. Here's what I've verified. 1. Fan works (tested with battery charger) 2. Relay works (tested by jumping to gnd, fan turns on) 3. Continuity between the ECU rd/gn wire and relay. 4. If I jump the rd/gn to ground the fan turns on immediately. 5. Turning on A/C does not cause the fan to come on 6. Coolant temp sensor is working (Verified with OBDII logger and it's within 3 degrees of my gauge) From this I'm pretty sure the ECU is not sending a ground signal to turn on the fan.
VSS: I'm getting so signal from the VSS (as seen by ODDII logger) 1. Haven't started trouble shooting so I'm all open to ideas.
Any chance these 2 are related? I'm completely stumped.
Car #: #67
Year : 1992 Posts: 634
Dunk- Great car!
2 ideas... Check the AIM system to make sure you have 14.x volts when running. Maybe you don't have enough spark. #2 I think you should have allot more advance at full rpm. Probably more like 40deg. If you only have 22deg after 4000 then something is wrong.
Please post the final outcome. I'm building a '99 and it would be good to know the results. Actually, mine had a intermittent stumble at speed. Drove me crazy but in the end it was the ground strap from the PPF to chassis. You might make sure that is good as well.
-------------------- Oregon Region SM 67 Hershner & Bell Insurance Agency
Well, it was definitely a clogged pre-cat in the manifold. I'll get the dyno graph up later, but it went from making 105 with a clogged cat and no restrictor to making 115 with a fed manifold and the spec restrictor.
Not quite pro motor horsepower, but certainly better than it was before. I'll do a little more tweaking now that timing will be open next year.
Winter projects are coming along nicely.
I've added the fuel gauge, TPS, steering angle, and EGT sensors to the MXL. Also replaced both rear wheel bearings and swapped out the old cam bolts for new ones.
Also pulled off the valve cover to inspect and change the gasket (slight leak). While it was off I decided to spruce it up a little. Going with the overall theme.
Anybody have good pictures of a properly sealed up rear bulkhead. I have the aluminum plates from Miatacage, but was wondering what else needs to be sealed. I have all the factory access plates installed.
Thanks. Definitely looking forward to getting it on track in race trim. February NASA event will probably be the first. My list of winter projects is getting shorter.
- FPR install and dyno tune with 37mm plate - design and install ballast system (needs to b adjustable so I can run SCCA as well. - Align and scale - bleed brakes and change oil - Install new interior roof paneling on trailer.
Installed the Advanced Auto Sports Fuel Pressure regulator. Took less than 10 minutes. Thanks for a great kit Dave. Still waiting on a few parts to add the fuel pressure gauge. Will be inputing that into my data system as well.
Also, here's a picture of my steering angle sensor. I welded a bracket onto the crossmember to get the belt alignment perfect, and then slotted the installed bracket so I could adjust the tension. The bracket is tapped for 1/2-20 threads so I don't have to worry about nuts. 2 socket head cap threads hold the sensor in place. Very simple and easy to adjust.
I also calibrated the Iron Canyon Fuel Sending Unit. Using the online mode of the Pista I emptied the tank and filled it up 1 gallon at a time, recording the voltage at each step. I used this to build a custom sensor, which I calibrated to read in gallons. For those that were wondering, the stock gauge is very linear thru the middle range, less so at the edges.
Last thing today was to get the car on scales to weigh it. With zero gas in the tank and me with gear it's 2352, so I'll definitely need to add ballast.
I'm planning on building a modular system. I'll weld a plate into the floor of the passenger side with some studs in it to secure the other plates. Then I'll have stackable ballast plates. Should make it easier to convert the car to SCCA specs from NASA and adjust for the cool suit being empty or full.
I've got my measurements, just need to run some calculations to figure out the weights needed.
Region: SW Division
Car #: 32
Year : 1999 Posts: 194
Maybe I misunderstood your post - but you seem to be planning on installing ballast in the trunk? Please note that this violates GCR rules (page 602). Also pay attention to the fact that EACH segment of ballast must be fastened by 2 bolts. I recently was challenged on this during tech (I had 2 stacked elements held by 2 bolts and had to change it to 4 bolts).
Region: SW Division
Car #: 32
Year : 1999 Posts: 194
Cool. Be a bummer to have such a well prepared car rejected at tech. Fantastic job by the way.
Incidentally, are you installing a brake pressure sensor? I have both this and the steering sensor inputted in my Aim and find it very useful. I also installed a throttle sensor which puts an end to any debate about whether I am taking some corners "flat" or motor boating the throttle mid corner.