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Race engine break-in

Old 05-16-12, 01:35 PM
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Race engine break-in

can someone please enlighten me... if i have a engine and car specifically for racing not street legal by any means. how do i break in a brand spanking new engine? doing a normal break in is not possible so how is it done?

even if the engine was stock but was a fresh rebuild how do i break it in or prep it for racing with 0 miles on it.
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Old 05-16-12, 10:08 PM
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There is a series of steps you take a various rpm's, something like 5 hours total at a minimum. If you use the racing bearings you don't need to go through the whole thing. you can shorten it up with some dyno time too.

C&P from the mazda motorsports site.

Rotary Engine Break-in Procedures
A proper and careful break-in period for a newly rebuilt engine is extremely important. The break-in procedures listed on the following page may seem excessive. However, an engine that has been broken in properly will see more power across the engine's rpm range and longer service life than a comparable engine that has not. If using the old bearings, please note the difference in hours and mileage requirements for the break-in period.

When breaking in any engine (race or stock), use a low ash content, mineral-based racing oil (20W or 30W). After the break-in period, change to a mineral or synthetic racing oil (30W or 40W).

Race Engine Break-in Procedures
The information provided in this catalog is intended for use by individuals with some knowledge of rotary engine rebuilding. There are many experienced high-performance rotary engine rebuilders across the country. Please contact us for the locations of these shops.

Race Engine Break-In

Using a dynamometer for engine break-in is preferred. If you do not have access to a "Dyno," use the mileage break-in figures on the following table. The engine should first be run at idle for 30-45 minutes. During this time, be sure to check for leaks and keep an eye on the gauges. Ideally, for the first 100 miles (depending on use of new or used bearings), avoid operating the engine above 5000 rpm or under heavy load.

From 100-200 miles, gradually increase rpm, but never allow the engine to approach red line. Beyond 200 miles we recommend only short bursts of power approaching red line for 100 miles. At this point, change the break-in engine oil. The engine break-in period is now complete.

1500 0.5 - - -
2000 0.5 0.5 - -
2500 0.5 - - -
3000 0.5 - - -
4000 1.0 0.5 - -
5000 1.0 0.5 60 -
6000 1.5 0.5 60 25
6500 1.5 0.5 - -
7000 - - 60 25
8000 - - 60 25
8500 - - 60 25
TOTAL 7.0 2.5 300 100

Coolant Temperature
(Outlet Side) 160 - 175 F 160 - 195 F 205 F
Oil Temperature
(Oil Pan) 160 - 175 F 195 - 230 F 250 F
Oil Pressure
-Stock Pressure Regulator
-Early (pre-1979 Engines with
Shimmed Pressure Regulator
-Competition Pressure Regulator
70 psi @ 3000 rpm
80-85 psi @ 3000 rpm

105-115 psi @ 3000 rpm
Engine Compression
-(1976-85 Engines) Range for earlier
engine will be slightly lower.
-Difference between chambers should
not exceed 20 psi (hot).
105-150 psi @ (HOT)

80-100 psi @ (HOT)
(w/carbon seals)
Engine Timing*
(Factory Recommended Settings)

20 BTC leading
20 BTC trailing

*you need to follow along with the little dashes under the new bearing, used bearing, miles headings, the site won't leave the big spaces for the columns
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Old 05-17-12, 08:28 AM
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Do what your engine builder recommends.

Mine said pour oil in it and go make your dyno pulls. Within 5 minutes my new motor was seeing 9k RPM. It did fine, but of course it was balanced, clearanced, new seals, race bearings, etc. That was with 20w50. After the dyno, I changed the oil and filter and that was it. It makes good power and I have heard others say just go rev it.

Here is a link to the Mazdaspeed info jgrewe posted above http://www.mazdaspeeddevelopment.com...g/techtips.pdf
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Old 05-17-12, 10:05 AM
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Thank you very much guys!
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Old 05-19-12, 06:14 AM
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My engine builder told me to do a 20 mins session on the track with varied loads and revs, building towards running it at about 90%. After that, change the oil and ready to go racing.

That was 14 months ago - motor runs perfectly ...
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Old 05-19-12, 10:10 AM
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really depends on the apex seals used and the bearings. If your using new or burnished bearings and aftermarket seals your break in time will be drastically shortened. In the last RX-8 engine I built using Goopy Seals and used bearings we drove it around the block a couple of times and that was it, we loaded it on the trailer and the next time it was started it went out on track for the practice session at the Miller World Challenge Race.
In my S6 Turbo motor using Goopy apex seals (2mm) running on E-85 there was no break in at all, I started it up, drove it on the trailer, and autocrossed it the following day. When I got back the compression (at 5280ft plus elevation here in Denver) was 115 on all faces, and climbing.

If your using more "conventional" apex seals, like Mazda OEM or Atkins, or if using carbon or ceramic seals, then the break in may be longer or shorter. Also if your using Cermet or similar treated housings, you will need to follow their specific break in instructions using the seals they recommend.
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Old 05-22-12, 07:29 AM
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I don't get the point for longer break-in periods if new bearings are used.
Those bearings are journal bearings, there is no need to brake something in, because there is no metal to metal surface contact!
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Old 05-23-12, 09:48 PM
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The reason for the longer break in is when the bearing is pressed in it will usually have high and low spots which the process of running the motor burnishes the bearings in, for lack of a better description. There is a technique to burnish the bearings in using special equipment, but very few shops out there has such specialized bits on hand. Using a hone is NOT the answer, before someone gets that bright idea.
IF you install new bearings and run the engine hard out of the gate you will very likely have some issue with the bearings, which experience has shown to be overheating followed by seizure, necessitating at best repolishing the eshaft and a new set of bearings, with much worse alternatives.

Also, if your planning on beating the crap out of the engine (esp in a race or drift car that will see high oil/water temps) do yourself a favor and follow some advice from Mr Hanover over n the sans pistons forum-

Just as with the magic tab, the locktite will not prevent a bearing from spinning that has welded itself to the crank. If a person were to hone out the bore just a bit, and sand out the bearing ID with some 600 silicone carbide paper in solvent, to get a bit more clearance, then you want to add some help for the lost crush fit.

The loctite also helps make a thermal conductor. Some rotors have dismal machining in the bore ID. As though they were done with dull tooling. The Locktite fills those voids.
What he is saying here is to get the proper (slightly larger) clearance in a race engine bearing clearance to eshaft, you hone the rotor bearing out slightly (make it round) and then locktite the bearing into the bore. He follows with some other advice I have found key-

Well, honing will take away as much material as you want it to. It just makes for a nicer finish and a rounder hole.

The point of honing the bore of the rotor is to remove material so as to increase the bore size, so as to increase the bearing bore size, so as to increase the bearing to crank clearance. While doing this you loose much of the crush fit of the bearing. So, you loctite it at the minimum and it is real smart to drill and tap holes so you can bolt the bearing in place with flat head (socket head) screws. Three per end works fine. Removing the indium overly eliminates the flowing of indium at very high temps, so you cannot loose the bearing from locally overheated oil.

Oil temps in the wedge may be astronomical and even though the actual amount (volume) of oil is tiny, it is a major sourse of oil temperature.

If you press a new bearing into a rotor (more likely on a lightened racing rotor) and it goes in real easy, better check the bore diameter to see if it has been enlarged. (you should have checked it already)

There should be screw holes to give this away, but not always. The very smooth finish of the modified bore would also be a clue.
These are key points when assembling an engine for racing.
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