LocostUSA.com

Hello guys,

I'm asking myself what kind of engine is more reliable for track use only. It's obvious which engine will deliver a better performance/weight/price factor in most cases but that's not what I want to speak about. I'm also fully aware of every other general pros and cons (bec. vs cec), that's why this shouldn't be debated here.

I read through many forums and noticed that many seven type bec builds had problems with engine failures, most of them used the hayabusa engine in a westfield. But what is the reason for this? I continued reading and there are basically three theories which are linked to oil starvation but no one has a concrete answer:

1. Bike engines can't withstand and were not designed for the higher G-Forces during cornering which you can reach with four compared to two wheels.

2. The hayabusa engine is mounted longitudinal in all seven type builds but was developed for a transverse application.
Therefore the hayabusa engine can cope with high G-Forces with a proper drysump kit and in an transverse application only e.g. Mid-engined locost (XTR2 or others). The reason for this is that the engine will experience forces which it was designed to cope with, if mounted longitudinal different forces will influence the engine which it can't cope with as well. (The longitudinal hayabusa V8 mounted in the Radical SR8 has a different block, so it isn't comparable to a stock engine)

3. The westfield dry sump kit isn't up to the job if used for the track only and it doesn't matter how the engine is mounted or if it is a bike engine or not.


Basically I want to decide what engine will be cheaper as a long term solution with many, many miles on the track. A 200hp+ NA Duratec engine or a stock hayabusa engine, let's assume both engines have a proper dry sump kit installed.

Furthermore I read that many guys are overhauling/refreshing their hayabusa engines, although I read on bike forums that many covered 60k miles on a stock hayabusa engine without an engine overhaul. I assume therefore that the lifespan of a bike engine is beeing significantly reduced in a car application? What kind of overhaul intervalls can I expect for a hayabusa engine which is beeing used with four wheels on the track only ?

Is there a specific reason linked to reliability why only car engines are beeing used in the Westfield Race Series in UK and NL?

This thread was also posted in these forums:
http://www.locostbuilders.co.uk/forum/9 ... pid1315359
http://boardroom.wscc.co.uk/cgi-bin/iko ... =89886;r=1

1. Bike engines can't withstand and were not designed for the higher G-Forces during cornering which you can reach with four compared to two wheels.

It's not the amount of g forces, it's the direction. Bikes lean in corners so the cornering or lateral force is always perfectly downwards. Take that engine, turn it sideways and it may starve for oil when under braking especially. Braking would usually produce the highest g loads and the engine is likely at redline at the end of a straight.

I think the three points are inter-related and the above answer fits all. I can't speak for wether a certain dry sump setup works or not, but that would be true of any engine. They all must be properly lubricated and many engines have their own answer according to what fails.

The lifespan of an engine for racing has to do with how hard you run it. Essentially all engines are modified until they can no longer run reliably for more then say about 10 to maybe 15 hours... The variation comes from rules and pocketbooks. The bike engines are close to this limit in stock or nearly stock tune. Street use just doesn't add up to many hours at redline, like a track where all the time is spent at wide open throttle near redline. The abuse factor skyrockets in track use.

I think a Duratech at 200 HP may be a pretty conservative setup and should last a long while, perhaps 30 to 50 hours of track use. It is almost certainly more fun to drive the car then purchase and build engines, unless your an engine builder...

The race series likely specs a car engine for reaons of cost and availability. Were they to choose a certain bike engine, the pool of available engines would likely dry up and/or become expensive. Also depedning on the rules they may limit power a bit to add lifetime to the engine. If your in a series it's a nice thing if you can get a season or two out of a motor, compared to lugging a spare around - that's a big difference in budget.

Welcome,

I see horizonjob answered while I was tying.

I think you answered you question sort of. you stated:

although I read on bike forums that many covered 60k miles on a stock hayabusa engine without an engine overhaul. I assume therefore that the lifespan of a bike engine is beeing significantly reduced in a car application?

While many Hyabusa reach 60K (on a bike) there can be no arguement that in a car, that life is lessened due to the extra power needed more often. Now add to that, a lot of these BEC Locosts are on the track under more extreme demands, life is shortened even more. I don't have experience with the bike engines, but it just makes sense to me. Now compare that to a std Duratec engine. Many of them reach 160K in a much heavier car than the locost. Put that in a lighter car and the expected life should increase. Put that car on a track and things naturally go downhill. That is presuming that both engines get the required lubrication.

It would seem to me that if reliability is your number one priority, that decision has already been made. BUT that may not be the right priority for a dedicated track car. It may mean that the lighter, faster shifting Hyabusa (or other BE) be the engine of choice and just prepare for regularly scheduled rebuild/replacement. Priority for me would mean that the car fit into the racing class that you can locally compete in whichever engine/vehicle design that is.

I did more research and found out that powertec/radicalperformanceengines are granting a 40 hour warranty on their
1300cc hayabusa engines which are developing 230hp (+27% more power compared to a standard engine).

This probably means that the engine should get an overhaul/refresh arround every 40 hours.


The main differences compared to a stock hayabusa engine seem to be:

- Forged high compression pistons
- Forged rods
- Race ported and polished cylinder head
- Reprofiled high-lift camshafts and adjustable sprockets
- Titanium valves and retainers
- Race valve springs
- Dry sump system


If we have these values as a starting point, how many hours do you guys think a standard hayabusa engine could handle on the race track? I imagine definately more then the radical engines due to standard parts and a lower hp output of the same ccm.


@ horizenjob

I assume that a 200hp Duratec should be able to hold up much longer then the 30-50h which you stated as radical bike engines can already withstand 40h on the track?

Other factors to consider when asking this question are the level of preparation and planned driving style for engine.

Both car and bike engines can be built, tuned and stressed within in an inch of their lives before the vehicle they will be used in ever sees a single lap on a track. Some race engines (car or bike) are built with very wild (compared to street use engines) combinations of loose lower end bearings (that over a few minutes heat up to settle in for minimal drag) combined with really snug rings designed to take maximum advantage of each combustion event. I've seen engines built to the point where they sounded like they had bad bearings (when started cold) that needed 5 minutes or so of warm-up before they could be loaded (and the car put into gear). Usually the lifespan of an engine like that is measured in only a hand full of races.

Also typical RPMs will play a huge role in how long an engine lasts. I've seen charts showing acceptable bike engine wear (delivering peak power) being measured as around 6-8 hours at redline, but something like 20-30 hours at 300 RPM below redline. And listing months as the wear life when the RPMs were cut by over 2,500. Those figures were based on sustained use, not peaks. Car engines also have a similar curve, but I'm not sure if it's quite as steep at the bike engine curve.

Here's a gross oversimplification, but I suspect heat also plays a very important role in the engine wear process. While engines are air pumps, their primary waste product is heat. The more mass (and better cooling via water, oil, air, etc.) they have to be able to absorb and dissipate that heat, the longer they generally seem to last - in essence, not unlike a brake rotor.

Rx7locosts's coment about building the car (and choosing the engine) based on the rules is dead on. If you are building for the track, sort out your class now and just build to the rules. It means you are already most of the way there if you decide to race or you have a class legal race car to sell if you don't.

After speaking with duratec engine specialists, bike engine specialists and some drivers who are participating in races with these engines I managed to gather some information:

Rebuild intervals for race applications:

Duratec 200hp rebuild intervall: 50-60h

Powertec 220hp hayabusa rebuild intervall: 40h

Refreshed standard hayabusa engine: ~30h

Not refurbished standard hayabusa bike engine out of a bike: ~20h (will mostly fail due to a rod going through the block)


Be aware that these numbers will greatly expand if you use these engines in a road going kit car.

Therefore you can't really rule out any of these engine types especially as both of these engines will deliver nearly the same power/weight ratio in a seven type car.

Keep in mind 40 hours of tracks use is a lot of time measured in events or practice sessions.

I think the times probably border on generous especially for the bike engine, but that just might reflect people choosing to shift just a few hundred rpm higher. These numbers probably come from a small amount of data.

We have had discussions on this site about durability etc. Try searching for "piston speed". Here is a thread. The first page is sort of a low point for this site, but there is some info in the second and third pages...

http://locostusa.com/forums/viewtopic.php?f=4&t=5856&hilit=piston+speed&start=30

Yep. I was once interested in entering the 25 Hours of Thunderhill, and so asked my engine builder about using my 4age Atlantic engine. He advised that if I shifted at 9500 rpm instead of 9800, the engine would go twice as far between overhauls. If I shifted at 9200 the engine would go "forever", but I wouldn't win any races.

In the thread I pointed to they give a rebuild time for bike engines in DSR as 6-10 hours. People that are going for the extra 300 RPM to win races...

It really is hard to get exact info. People's dynos probably produce somethine like %10 variation, which accounts for 20 HP in the range your looking at. Some of it is intentional, some not, it kind of depends on who your dealing with. I have a friend with a dyno shop. people bring in motors to rebuild or tune and they don't make what they were sold as. Happens regularly. I suppose the easiest way to get big power is go back to the original shop that told you a big number...

Here is an overview which I found in one of Radical's user manuals (SR4).

The total cost except an engine and gear drive rebuild, brake discs, damages to the fuel
tank is 5365,00 GBP if all the stated parts have to be replaced/rebuild after the mentioned amount of "hours".

Radical also says that engines which are not being raced will hold up 90 hours.




However I'm asking myself why the front and rear uprights have to be replaced, a bearing change would do the job?

Furthermore the front and rear wishbones have to be replaced too, although a change of the spherical and rubber bushings would do the job as well?

Designed for a fatigue life maybe or if the bearings were staked in place you may not be able to change them?

Not to doubt their engineering staff but if it is for fatigue reasons, I would like to see their data. Multi billion dollar companies with ginormous engineering staffs and a ton of good empirical data have a hard time getting the fatigue stuff 100% accurate - I doubt a much smaller race car manufacturer will do much better. Then again maybe its a CYA sort of deal? When it fails and you didn't replace it, "we told yinz so".

The only reason which I can imagine is that the uprights and wishbones were designed with compromises due to weight savings?

If these parts would be designed to last as long as possible then they would simply be much beefier and therefore heavier?

The Radical is essentially a pure race car, despite being able to be made road legal in the UK.

I suspect the service intervals are for those aluminum bits are spec'd out for a combination of CYA and "We like to sell replacement parts." I'm also a bit of a cynic, lol.

I have to agree with you, it looks like Radical's aren't the best bang for the buck and they seem to generate a good part of their turnover with replacement parts and engine rebuilds.

Maybe they perform ~20 % better then other mid engined kit cars but for a 100% price addition in the purchase price and the runnning costs.

The competition drivers may need these 20% but I think radical's are too expensive for track day drivers like I am.

There seem to be cheaper mid engined kit car options which perform nearly as good for a much lower price (purchase+maintenance).

You can put me in the cynic camp with Erioshi. However:

I have to agree with you, it looks like Radical's aren't the best bang for the buck and they seem to generate a good part of their turnover with replacement parts and engine rebuilds.

I hesitatet to slam the Radical folks though. It's a race car and those intervals seem appropriate. If you want bang for your buck, you have to be careful what your looking for. If you want to win races, you need something that will do that, anything else provides no bang whatsoever - except to your wallet.

I can't thing of a 30-40 hour interval with my Formula Ford that didn't involve collisions with cars, walls or trees not to mention the occasional trip thru a meadow at 70 or more MPH. When I bought my cars, I tore them down to bare metal and had lots of bits magnufluxed or dye checked. I also went thru the frame carefully. I have found a cracked rear stub axle and frame cracks. You really do depend on things working on the track and the things I mention must be done or your taking risks. Taking risks is not a long term solution.

Having something a little sturdier for your use may well be a good idea, but you will need to follow a similar inspection schedule. No need to use the very smallest rod ends or the narrowest tube for your wishbones. Small differences in size there make a big difference in strength and safety margin.

I'm not sure of your intended use, but finding a class you can run in with other people will add to your enjoyment. There is a lot to be said for the comraderie and help/advice you can get from a popular class. If it doesn't cost a fortune that will add to it.

It is a very good idea to seek something that will work well and that rules out street cars in all forms except for a small minority like the Seven or Locost. When I first drove an old Formula Ford in about 1980, I was sold within a 100 feet of driving. It just worked so well, I was finally driving and not herding! I think Seven / Locosts are in a similar territory, very light and responsive with brakes and steering that actually work and reasonable service life of components...

Good luck!

If you are looking at track use, look at the many people who have run the engines. A few in the UK have run the Hayabusa motor without issues, but they once a year either put in a fresh motor or rebuild.

Then there are the nuts who try to ring every ounce of power out of it, by over boring etc. The 1500+ hayabusa motors produce alot of power, but they do not last. It all depends on what you do to the motor. At the same time if you take duratec and push it to the limit say 300+ hp, it will also fail.

If you like the busa motor, heck just buy a spare one. They are pretty easy to swap out.

Simple. The bike engine will not last as long they don't on a bike. More than double the weight to push
around and it has to work a harder. So yes given the same power output the bike engine won't last as long.
I suspect a Busa engined car would last a while on the street. Longer than a R1 or GSXR1000 motor for certain.
But not nearly as long as a 2.0 Dura/Ecotec.
Bike engines tend to have smaller bearings and are built with one eye always on the scale

Stressed out race motors?

All bets are off.