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My IT7 car feels slow, obviously it's not suppose to be a rocket but I feel as though I'm down on some HP.
It's all stock minus a header/exhaust, some fancy looking plug wires, and that's about it!
At Road Atlanta it will hit 103-105ish down the back straight before the braking zone into 10.
The car revs smooth and seems to run fine, just lacks some grunt, then again it is a 12A. :p
Is there anything I can do to gain a few horses in straight line grunt?
You need to do a compression test to check on the baseline health of the internals. If those numbers are solid, then you can hit the dyno for some tuning.
One thing to factor in is your frame of reference. Your car will feel like a bullet when you are out there with ITB and ITC cars but will seem sluggish when with ITS and ITA cars. Just perception.
The bottom line is that you don't know if you are down on power and you need to figure out where you are at before you start throwing money at building more on what could be a shaky base.
Andy has it right. You need to check the compression and go from there. He's also right about being fooled by who you run with. However, a good ITB will run a 7 pretty even down the straights, with the 7 only having an advantage near the end of the straight.
With all that said, if all you're seeing is 105 at Road Atlanta, you are almost certainly down on power. I'm hitting almost 120 at the turn 10 brake marker. However, that includes about a 6-7 mph boost on the last downhill part of the straight - if you stop looking at the top of the hill, you'll think you are slower.
Cool I'll do a compression check and see what the numbers are. If the 12A is going bad though I'm not sure what I'll do. :shrug:
Aside from good compression, what else can be done? I've read a lot of people ran the Paul Yaw carbs but you can't find those much anymore, so I'm guessing by reading the GCR the biggest performance will come from a really good carburetor?
Of course the car still isn't as good handling wise as a well prepared IT7 and the driver is still learning but...:p
I do stop looking right after 9 but that would still be quite a ways off from your speed. Actually at the HSR event I ran I was going faster down the front straight than I was on the back straight from the shoot through 12. lol
Find a friend who is a front runner in the same kind of car and ask if he will share data and then buy the same kind of system. It used to be we all said shut up and get seat time but if you can compare data you will not be guessing If it is the car or the driver.
How the timing is set will have a huge effect. Has this been checked?
If the car "was faster", than you definitely need to do a compression test.
If it never was fast, than it could be timing or tuning.....or compression (seals) that has been bad for a long time.
If the motor is the issue, you can have a 12A built. They don't make the housings anymore, but there are still a lot of them out there.
The car was never faster than it is now, I have only ran it twice and power wise it felt the same. We had some transmission issues at the ARRC though so my time driving was spent fumbling with that versus really paying attention, but mph down the back straight was the same in both events.
I have not checked timing, I'll look into that, still pretty new to the rotary so I'm still learning. lol
I plan on doing a compression test this upcoming week.
Do you know how to do a rotary compression check? You can find the highest reading of the three faces with a standardly configured compression tester. But in order to check all three faces/seals you need to remove the schrader valve and eyeball it while cranking.
Yep found a little how to video today for rotaries when I looked up on it. Thanks!Quote:
Originally Posted by Eagle7
Make sure that the plug wires are right also. Lead, trailetc.
Simon:
and now for the bad news, my ITC Car was keeping up with you on the back straight and I would have repassed you on the next lap, if you hadn't gone into the pits:rolleyes:
Oh I don't doubt it, it's only going 105 tops down the back straight and with an hour to go we didn't have 4th anymore. :pQuote:
Originally Posted by ITC69
I have a Yaw carb if you find yourself wanting one. PM me if you are interested. I also have a 7's Only tuned carb. I'm no longer using either since I've gone to a Weber.Quote:
Originally Posted by Simon T.
However, first make sure your engine is sound before you start messing with the carb. One thing you should check is to make sure both leading and trailing ignitions are firing. The car will run even if one of those has failed. Just attach a timing light to each wire going to the distributor cap, you could have a bad coil or igniter. Trailing ignition would cost you a bit of power, leading would cost you a LOT of power. Ask me how I know. :rolleyes:
Simon, go through the basics. All good tips above. It will even run if the rotor is hooked up backwards, but it won't hit 105 that way LOL.
NO MATTER WHAT, make sure you have effective cooling for both water and oil, and that you have proper oil pressure. Don't forget to either premix or make sure teh oil injectors are injecting. it'll warp the apex seals in no time without proper lubrication.
Check your compression. Get Eckeridge :D to loan you a strip recorder. (If you use a normal comp tester, have a friend help while you watch the gauge. As mentioned above, remove the schrader valve to watch it "live".
Here's the code: One pulse (of three) significantly lower than the others, it's a bad side seal. Two pulses low, it's an apex seal. (Generally!) Problems are usually most common in the rear housing. If you find lopsided compression, don't freak, it likely can be rebuilt. But don't run it on the track until you do, or the thing will totally let go, shoot the seals out the exhaust, and take the housings and side plates with it. THEN you're up the creek. A new seal kit from Mazdasport runs a bit over a grand. Puuuuulenty of rotary rebuild knowledge in the Atlanta region.
OK, if the comp is even and decent, then it's time to tune. See if you can't find the old Yaw manual...just to read up and familiarize yourself with a rotarys' carb needs. You'll need a good pressure regulator and fuel pump. (The Hollley 7psi is a cheap/good choice) and you'll need to tweak the carb. It's a bit of tuning, and work. best done on a dyno. Take notes! The jets you need at the ARRC will be far different than a July day at RA.
Jeff Ryans car always had a tad more juice than mine on the straights, but he beat me in the esses, handling counts there and I had an odd transitional oversteer issue there. I was seeing 120 tops into the braking, according to my data.
Gearing will affect that, a tad. I ran 45 series tires with 4.88 gears, with a full airdam, but no splitter, when I recorded those speeds..
Don't expect 120 without a lot of tweaking and tuning. Cold air, cold fuel, etc etc. But 115 should be possible.
For a rotary, the exhaust is critical. Make sure nothing is crimped or blocked.
Thank you all for the tips!
I had wanted to do a compression test sooner but I'll get to it this week as things have calmed down.
Speaking of exhaust, it does have a muffler on it right now that came on the car. It was putting out surprisingly low db levels at the ARRC (between 86 and 88db) so I may take that off and see if it runs a little better, not expecting huge results but...
Thanks again, I'm hoping to find some mph this season, I don't plan on any ARRC wins or anything like that since it still has the watts linkage and just Tokicos and some unknown springs (whatever they ran in Pro7). lol
86db is reaalllly quiet for a rotary. You CAN make them fast and quiet, but you need the right parts.
Easier to make them slow and quiet. I'm going to guess yours is the latter. Proper exhaust should wake it up a bit.
Regardless, do a compression test regularly to track it's health.
One other thing to think of is the carbs/secondaries.
Was talking to a guy last weekend about his 12A, and he was complaining of low power too. He even went to the point of having the engine rebuilt and still no more power. eventually something happened and he tore the carbs apart. there was a gasket in there "upside down" or something that was blocking one of the tiny internal vacuum lines. This just happened to be the part that fires off the secondaries.
fixed that gasket problem and VOILA!
X2 on the carb deal. I am pretty sure that you can over ride the vac can with a couple of rubber bands to open the secondary plates. Not sure how legal it is for your class.
Another carb related issue that I have encountered is a bad diaphragm on the secondaries. When that happens, you get little or no opening of the secondaries, which as you might expect, seriously reduces the power level. You can check that the secondaries are opening fully when you run on the dyno. Or you can find a major leak by taking off the vacuum chamber and sucking on it to see if the rod that actuates the secondaries goes in as it is supposed to. BTW, don't try any of the suggestions that you make the secondaries operate mechanically. That's one thing that has been specifically deemed verboten, and SEDiv tech inspectors occasionally do check secondary operation in impound for IT7s.
FWIW if the engine will start easily, the compression is usually fine. The more common weak power problems are the carb, one/both of the dist wires out of phase, restricted exhaust.
If the car is quiet, take a peak inside the pipes.