basic questions

[tbtapper]

Not looking for any "secrets" from anyone just trying to get some base lines.

Just started ITs with a very nicely preped RX7.

Car runs great seems to be very competitive in over all speed. (too bad I'm not up to speed, Yet!) Don't know too much technically about the rotary so I have some questions.

Questions are this: On the 13b motors what sort of rpm shift points are folks running?

What sort of water/oil temps are folks looking to maintain??

Opinions on ratios on premixing (no oil injector) and opinions on lube. (Mo1, dino ... )

Any specific areas to watch out for like transmissions, rearends, brake rotors etc.

For me this is a hobby. Basically an "odd" way to relax.

I'm realistic about being competitive with folks that have raced for years and work in collateral industries.

I want the car to last reasonably long given the use. But I don't want to always be the backmarker either.

So any baselines that you experienced racers are willing to give me would be really appreciated.

Thanks

tbtapper
RX7 no.9 ITs

[Mike Spencer]

You won't get any "secrets" from me, since I'm new at this too and don't have any!

I'm sure others will chime in with more specific info, but I can offer a few basics.

First, you probably won't be a backmarker (after a little seat-time) no matter what. ITS typically runs with other slower classes and the RX-7 is a strong car in that class (the E-36 BMW notwithstanding).

I shift my 12A at about 8-grand. It will spin higher, but the "nut behind the wheel" is still the weakest link and I don't feel the additional RPMs are worth it (speed vs. wear). Others more knowledgable will probably have other opinions. I'm just being "safe".

re: Pre-mixing. Do NOT use synthetic. It leaves residue you don't want. A good quality dino oil is best. (opinions re: which is best vary WIDELY)

As far as "weak" areas, Mazda transmissions have a bad reputation. They need to be shifted with your wrist, rather than your forearm. I honestly don't know about 2nd gens, but rear-end ratios in 1st gens are generally high 4's or even low 5's. (Running a stock rear-end ratio COULD cause you to have slower times)

Speaking of ratios, the 2nd Gen came with 3 (I believe) different 5th gear ratios. The numerically highest is best (something like .81 as opposed to .78), although depending on the track you may not ever get INTO 5th.

One final thought. Overheating a rotary will KILL IT! I would shut down halfway through the last lap if the engine temps started climbing. Trying to "nurse it home" to pick up a $10 plaque (to me) isn't worth the price of a new engine.

I'm obviously biased, but I think you picked a great car. I hope you enjoy it!


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Mike Spencer
NC Region
ITA/7 RX-7 (finally)
1990 RX-7 Convertible (street car)

[dyoungre]

I'm most familiar with the 12A (from a racing standpoint). Temperatures: Oil max should be about 200, and water around 185. You actually start losing power much above.

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Dave Youngren
NER ITA RX7 #61

[Mike Guenther]

Tapper, here's all my secrets;
*My shift light comes on at 7800 and I shift somewhere between 7800 - 8100, rarely over that.
*Water temp is usually 190 - 200*F
Oil is between 220 - 240*F when I come off the track.
*The 4:88 is a common rear and the 5:12 is desirable at many tracks - I'm still looking for a 5:12.
*I heard that synthetic lube works better at a pre-mix than non-synthetic because it doesn't get broken down in the gas and gives better lubrication at higher temps. I use regular oil Valvolene VR1, 20w50, in the crank case with the lube metering pump plus a pre-mix of Amsoil synthetic. Haven't had any build up problems I know of.
*The transmission IS the weak link. I have one rebuilt about once a year by Mike VanSteenburg at www.iscracing.net
*Be safe and have fun -
Mike

[ddewhurst]

Mike G., I am in the process of converting from Spec-7 to ITA/7. Went out this past weekend & the trans is stuck between 3rd & 4th. At this point I have new header/exhaust, radiators, carb & rearend. Shifted in Spec-7 at approx 6,800 rpm. Shifted this past weekend at 7,800 (pulls great up till 7,800) & the thing stuck while going to 4th & wouldn't go into any gear.

How many races do you do with the Mike Van rebuilt tranmission before rebuild ?

Thanks
David

[Mike Guenther]

Dew, I usually race about 8 weekends per year. When I was in IT-7 I always kept a spare transmission ready because once they start going it can become worthless fast. At my race school I accidently down shifted into reverse in the race at the end of the first day. I lost 5th but finished the school. VanSteenburg rebuilt that tranny and also made the shifter feel a lot more accurate. He modified the forks to make it a bit stronger. With the second gen I shift at higher RPMs than with the first gen. I have only had the 2nd gen for a bit more that a year but have had the tranny rebuilt once already. It is giving me a slight grind now whenever I down shift into third, so I know it will crap out sometime soon. I'm trrying to be patient with my downshifts to make it last awhile. Typically I have been getting a year between rebuilds.

[Mike Spencer]

Originally posted by Mike Guenther:
...*I heard that synthetic lube works better at a pre-mix than non-synthetic because it doesn't get broken down in the gas and gives better lubrication at higher temps. I use regular oil Valvolene VR1, 20w50, in the crank case with the lube metering pump plus a pre-mix of Amsoil synthetic. Haven't had any build up problems I know of.

Mike -

No temper tantrums, just genuine confusion. I have heard that using synth in pre-mix is a big No-No for YEARS! Is this a new product you speak of?

BTW, one of the places I've seen information about this is; http://www.bacomatic.org/~dw/tech/tech.htm


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Mike Spencer
NC Region
ITA/7 RX-7 (finally)
1990 RX-7 Convertible (street car)

[Mike Guenther]

Mike, I was told by Carl Sloan of SAS Racing, www.sasracing.com , when I bought a newly rebuilt first gen motor, that the petroleum oils completely break down in the gas if you premix. They have some chance to lubricate when injected into the gas just prior to ignition, but pre-mixed they are completely dissolved and diluted in the gas. The synthetics don't dissolve as completely in the gas and therefore have better lubrication capability when used in a premix. It made sense to me. Since I was giving him over $4 grand for the motor, I thought I better take his advise and follow his instructions. Carl has a lot of experience with Mazda motors in every class and he would know if there were problems with build up, sludge or whatever when he opens up the motors he builds. I've been doing it the way he told me ever since. Now I have a 2nd gen with injectors and I still pre-mix with synthetic. No problems yet.

[Mike Guenther]

One other thing about synthetics. I had a great 1977 Pontiac Firebird that I drove very hard for over 250,000 miles on Texaco Haveline 10W40. With about 30,000 miles on it I let a shop talk me into trying a Mobile synthetic on an oil change. I drove it about 50 miles and it was tapping so bad it was scary. I dumped that rather expensive synthetic oil and put in the Haveline. I sold the car with over 250,000 miles and it still ran like a champ. A complete chassis rebuild, new A/C and a couple of custom paint jobs, but only one tune-up and spark plug change and no engine trouble ever in over 20 years that I had that car. Needless to say, I'm no fan of synthetics in the crank case. I use Haveline 5w20 in my V10 Excursion. 80,000 miles in the last two years. I used to use only Haveline in my race cars also, but Carl Sloan said he preferred Valvoline VR1, so I've been using that in the race car for the last few years.

[cpa7man]

Originally posted by Mike Guenther:
Tapper, here's all my secrets;
*My shift light comes on at 7800 and I shift somewhere between 7800 - 8100, rarely over that.
*Water temp is usually 190 - 200*F
Oil is between 220 - 240*F when I come off the track.
*The 4:88 is a common rear and the 5:12 is desirable at many tracks - I'm still looking for a 5:12.
*I heard that synthetic lube works better at a pre-mix than non-synthetic because it doesn't get broken down in the gas and gives better lubrication at higher temps. I use regular oil Valvolene VR1, 20w50, in the crank case with the lube metering pump plus a pre-mix of Amsoil synthetic. Haven't had any build up problems I know of.
*The transmission IS the weak link. I have one rebuilt about once a year by Mike VanSteenburg at www.iscracing.net
*Be safe and have fun -
Mike

Mike hit it on the nose.
My water temps saw 210 4th of July weekend, oil temps 220 or so.
I run AMSOIL 2-cycle as well(premix 1oz. per galloon of fuel). This past few races I put AMSOIL 20/50 racing in the crankcase. I think it ran better on the Valvoline VR-1 that I was using.
I'm having some shift issues as well. Missing 2-3 shift more frequently.

Good luck the ITS RX-7's are fast. Most races they lap me at least once.




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Paul Pineider
ITA 05 (Soudiv)

[Festus E. Simkins]

Well, here's another opinion. Mine is a 12A that is a factory authorized rebuild, i.e., iron apex seals. I typically shift at 7500 to 8000 rpm. It has seen over 9000 rmp a few times. Mechanical overrev, i.e., 5th to 2nd gear. And once in the heat of battle I forgot to shift. I was wondering why I lost power. When I looked I was at 9300 rpm. Engine lived but it really got my attention. I premix 1 oz to 1 gal of 87 octane gas. I use Yamalube "R" synthetic. I have been running the motor since 1996. It has seen 225 Degrees F for an entire race. I really get worried if it gets to 220. Usually run between 195 and 210. I run 10w40 Castrol dino oil. I change every 3rd weekend. I have been using the same transmission that came out of a 100,000 mile car since 1996. It needs a rebuld. It is hard to find the 5th to 4th downshif or 5th to 3rd down shif if you get in a hurry. If you shift it easy no problem. Try and shift real fast and you get "hang up."

I have talked to acouple of guys that have race built motors with carbon or ceramic seals. They are routinely twisting 9300 rpm and running 512 gears. I really don't know their rebuild schedule.

That's all I know.

Drive well.

[tbtapper]

Thanks for the replys. Always interesting opinions when lube comes into the discussion.

I don't know what type of seals I have. I have found the builder. Just waiting for a call back.

My engine seems willing to pull well past 8k but I'm guessing I'm into diminishing returns and much quicker trips to the rotary doctor.

I'm a little unclear on the premix scenario. Seems like some folks are premixing AND running the factory injection setup.

Would this not put more oild than neessary into the combustion chamber. I premix oil with the gas at 1oz. to a gallon.

This seems pretty common but I do NOT have a functional factory injector system. If I'm way underlubing let me know.

Guess I'll stick with Mo1. Always used their products in everything I own with apparently good success.

[Mike Spencer]

Originally posted by tbtapper:
...I'm a little unclear on the premix scenario. Seems like some folks are premixing AND running the factory injection setup.

Would this not put more oild than neessary into the combustion chamber. I premix oil with the gas at 1oz. to a gallon.

This seems pretty common but I do NOT have a functional factory injector system. If I'm way underlubing let me know.

Guess I'll stick with Mo1. Always used their products in everything I own with apparently good success.

Again, I'm a newbie and am just doing things the way the car's previous owner had done it. If this flys in the face of current practice, I would LOVE to hear about it!

I use both. This makes sense to me because I have heard/read in the past that the amount of oil required (whether injection, pre-mix or both) goes up with RPM. If this is true, one COULD surmise that the factory settings on the oil injectors would be for "typical" RPM range (like 3-4,000). Not the 7-8,000 we see.

As always, your mileage may vary...


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Mike Spencer
NC Region
ITA/7 RX-7 (finally)
1990 RX-7 Convertible (street car)

[Quickshoe]

I always used 1oz to a gallon premix only. No injection. Yes the stock injection does adjust for throttle position.

The premix will keep the oil/fuel ratio constant.

I utilized Blendzall. Never had any lube issues with it in all my years of racing air-cooled 2 strokes or rotaries...so must be pretty good.
With any castor bean based oil it will separate from the fuel when it is allowed to sit for long periods, the separation process appears to be expedited by cold weather. So, I always mixed it 5 gallons at a time and put it in the tank prior to running a session.

I did utilize Maxima 927 when I could not find Blendzall and was happy with it as well.

If you premix only you should be cool with Synthetic in the "crank"case.

I would use the best non-synthetic 2 stroke oil at 1oz to 1 gal. Synthetic in the crankcase with no oil injection.

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Daryl DeArman

[C. Ludwig]

Daryl, you've never found bean oils to leave deposits? The rap I always heard on them in my two-stroke days was they lube well but gunk up exhaust power valves and manifolds. But hey, they smell SOOO sweet!

I premix only. Throw back to my two-stroke days also. Though rotary injection pump failures are fairly uncommon I just don't trust injection pumps at all. Pre-mix and you know it's in there. Pre-mix @ 100:1 with Redline synthetic two-stroke oil. Mobil 1 in the crankcase.

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Chris Ludwig
08 ITS RX7 CenDiv

Originally posted by Mike Guenther:
One other thing about synthetics. I had a great 1977 Pontiac Firebird that I drove very hard for over 250,000 miles on Texaco Haveline 10W40. With about 30,000 miles on it I let a shop talk me into trying a Mobile synthetic on an oil change. I drove it about 50 miles and it was tapping so bad it was scary. I dumped that rather expensive synthetic oil and put in the Haveline. I sold the car with over 250,000 miles and it still ran like a champ. A complete chassis rebuild, new A/C and a couple of custom paint jobs, but only one tune-up and spark plug change and no engine trouble ever in over 20 years that I had that car. Needless to say, I'm no fan of synthetics in the crank case. I use Haveline 5w20 in my V10 Excursion. 80,000 miles in the last two years. I used to use only Haveline in my race cars also, but Carl Sloan said he preferred Valvoline VR1, so I've been using that in the race car for the last few years.

I lost a rotary after switching to synthetic, and lost another after swithing from castrol 20/50 to 10/30. there were other factors but I thought it was worth mentioning/

[Quickshoe]

Originally posted by C. Ludwig:
The rap I always heard on them in my two-stroke days was they lube well but gunk up exhaust power valves and manifolds. But hey, they smell SOOO sweet!

I didn't have any problems and that was at 6.5oz/gal which is a lot of oil. An important distinction--my 2 stroke racing was done in Piston Port classes, no reeds or power valves to gunk up. Carb rebuilds were a matter of routine maintenance anyway. Pumper diaphrams get tired pretty quick at 14,000+ pulses per minute.

Didn't have any issues in the 12A, perhaps injectors and operable 5th and 6th port actuators might be a legit concern.

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Daryl DeArman

[Boswoj]

Wow - lots of opinions and not much tech on this one! Synthetics are wonderful examples of modern technology, but also highly misunderstood. There are TONS of info on the internet written by people with Phd's in various engineering disciplines - it is really wothwhile to take the time to read them. For those of you on the short (attention span) bus, the synopsis is this:

In low load, non-critical applications synthetics and mineral oils perform very similarly. Mineral oils are refined from crude oils stocks and carry their natural molecular structure (plus refinement and additives)into the finished product. Synthetics have "engineered" molecules intended to produce a specific end result. It is when oils start reaching toward the outside edges of thsir operating parameters that the differences really start to show. Synthetics are designed to have more stable viscosities throughout their operating temperature range. They resist temperature related chemical change better. They "cling" or wet the surface to be protected better. I some cases, much lighter synthetics can equal the performance of heavier mineral oils, which allows less "churning" or parasitic drag in a gearbox or rear end. In some cases synthetics have superior heat transfer characteristics which allow vital parts to run cooler. Good quality mineral oil is still an effective and affordable lubricant for many applications. My personal feeling is that the one thing that will kill a rotary quickest is HEAT. Since synthetics generally cool better, help create less heat in the first place by having better friction characteristics, and resist vaporization, viscosity change, and breakdown better than dino oil at upper limit temps - I'm going to continue taking that extra bit of insurance for my expensive race motor. I am in no way connected to ANY oil selling or even touting one oil over another (and the short bus jokes were meant to be humorous - not piss anyone off!). Just for the record, I use either Mobil One for regular racing duty, or Amsoil for the hot week-ends, and I premix 4 oz to 5 gallons of Amsoil pre-mix oil with no injector pump.

Good Luck - hope to see you all Racin'

Boswoj

PS - not all synthetics are created equal either! Some are fantastic and well worth the extra dollars. Others are purported to not equal the best mineral oils so DO YOUR HOMEWORK!

[This message has been edited by Boswoj (edited August 02, 2004).]

[Tak]

Oil experiences.
I shared a house with two 125cc two stroke motorcycle racers (they opened the engines every 3-4 hours). Over two seasons they tried every premix they could find. Conclusions: Redline racing two stroke oil left the fewest deposits. My two season old racing rotary (complete ground up race build) with Mo1 in the crank and redline racing 2-stroke premix (with a functional stock injector--it's illegal to defeat it in IT FYI) had virtually zero deposits in the combustion chambers and seals, and no damage to the bearings after losing a water line and thoroughly overheating the engine. All the rubber bits were toasted and all the seal springs lost tension, but the bearings showed no wear. No indication of scuffing between rotor or side housings; no indication of rotor gear damage either.

Tak
#29 ITA
SFR SCCA

[mrbill]

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