I think I and others may have posted some info about run time versus load time for engine and GDU refresh for 1500cc SR3, as well as what to use in terms of the lifing of components. I want to set the record straight on a few topics that involve maintenance cost and performance of the SR3.
On my chassis SR301351 I had a Rekluse (spin-safe) clutch go out at about 45 hours of run time, 25 hours of load time. At that time I had convinced myself that the engine was timed out using the run time and not load time. I have since changed my view after talking to a Radical technician -- I now use on-load (over 4000 rpm) time for component lifing schedule and NOT run time. I currently have a SR3 with 60 run hours and 31 on-load hours. This one is running perfectly and the spin safe clutch still works well. A tech once told me that the 1500cc RPE engines should be refreshed at 40 hours on-load time, and that after 45 hours on-load time the 1500 is a ticking time bomb. I plan to refresh at 40 to 44 hours of load time. I think the 1340 can/should be refreshed at 80 hours.
There is a lifing table for components in the owner's manual; I now use on-load for lifing, and I typically adjust some of this based on my own experience. For example, I only service the axle tripod joints every 20 hours (on-load) instead of 10, but I also use GKN tripod grease which is expensive but well worth the extra cost. I service the GDU twice as frequent -- every 20 hours instead of 40 because I see early pitting wear in the forward gear and sometimes the large crown gear. I think it is OK to stretch the service of the GDU to 40 hours on-load but since I am familiar with the GDU and it is not a big job for me, I do it twice as frequent.
Engine refresh is expensive if you use a certified RPE engine rebuilder who seals the engine and uses the required RPE parts. My last Spring Mountain refresh cost $11k and about $1800 for round trip freight. For the 1500, you need those RPE specific parts. For the 1340, perhaps you don't, however if you want to race you need the official engine seals to pass tech inspection.
If you do the math, then every 40 hours of run (edited) on-load time (or 45 if you want to gamble), then you would spend about $13k for engine refresh and about $1200 for GDU parts if you refresh the GDU yourself. So figure $14200 which works out to $355 per hour just for the drivetrain. For consumables, brakes, tires, rotors, skid pads, body parts repair/replacement, fasteners, bushings, shock and caliper refresh, etc, etc., you could imagine at least $400 per hour to operate. Now this is my estimated cost and I drive the car very hard. I have seen other track-day cars and even cars that race which are not driven as hard and every component from the rotors to the body parts looks like new. Those cars will require less maintenance cost, but the engine refresh lifing is still 40 hours on-load time.
Tires are a big variable. If you race, then you spend about $3500 on tires for the weekend. That makes the refresh cost look pretty reasonable.
To be continued ...
Performance Comparison
The SR3 is a popular HPDE track day car and race car for several reasons. It has high downforce, is light weight, paddle shift, and has superb performance for the total cost of ownership. The Radical Cup race series is one of the very best for the cost because you get a lot more track time than club racing, and you get to go to events with IndyCar. It is an incredible experience at a much lower cost than SRO or IMSA.
A lower cost option would be to purchase a Honda Civic type R and do HPDE track events. There is nothing wrong with this option, although you won't get nearly the performance and thrill as a Radical or other race car such as a GT3, open wheel, prototype, etc. For racing, Spec Racer Ford and Formula Enterprise are lower cost options, but you will get much less track time than a Radical Cup event.
A couple times a year I will do a weekend with Chin Track Days or I will get invited to a club day. I did the two-day Chin event the weekend just before the Petit Le Mans race at Road Atlanta. There were several GT cars -- Mustangs, Supras, and Astin Martins on the track practicing for the race. I was a little slower, running about 1:27 to their 1:25-1:26 times, and this was in traffic. A better driver can do a 1:24 at Road Atlanta in an SR3 1500. There was a Porsche 963 on the track with us which can run a 1:10 or maybe a little lower. That car is a beast.
The Mustang GT3, built for IMSA GT3 race series, cost about 250k in 2017. (The updated FIA GT3 2023 version from Ford will certainly be much higher -- I would guess in the 400k-500k range.) Michelin race tires are $5k-6k per set. I think the GT Daytona Mercedes-AMG GT3 cars cost about $500k. The IMSA and SRO GT3 cars are faster than an SR3 at most tracks, but not by a big margin, and the cost difference starts at double the price of an SR3. The Porsche 963 cost about $3 million dollars which is why I don't have one of those. I would imagine the tire budget for the Petit race for that car to be somewhere around $65,000.
For street legal cars such as the Ferari, Lamborghini, Porsche GT3 RS and GT4 clubsport, Corvettes, McClarens, BMWs, ..., the SR3 is often the faster car on the track and easier/less expensive to repair. The newest 2023 Porsche GT3 RS is an amazing car but not cheap.
In summary, the SR3 is not the lowest cost option for racing or HPDE track day use, but the performance and thrill level is very high compared to most other options. Additionally, the Radical Cup race series is arguably the very best for the total cost.
The SR3 cannot be beaten on performance vs cost!
Interesting comments on hours, especially from a dealer, as I was fairly sure the factory still recommend on total running hours.
Worth keeping in mind that on load isn't just above 4000 rpm it is also 25% throttle so anytime spent on the brakes or cruising around isn't logged as on load.
I thought the newer cars did on load from wheel speed but I could have that completely wrong!
Worth keeping in mind that on load isn't just above 4000 rpm it is also 25% throttle so anytime spent on the brakes or cruising around isn't logged as on load.
I thought the newer cars did on load from wheel speed but I could have that completely wrong!
You are correct. In my ECU log book data, I have the following for on-load:
On-load engine speed (rpm): 4000
On-load throttle position(%): 25.00
On-load vehicle speed (kph): 48.3
@davidf, great write up… as usual. One item that I am not sure is correct is using on load time for engine overhauls. Although it is unintuitive, it is my understanding that Radical recommends using Total Hours for engine overhauls. I know that if you use extremes, this doesn’t make sense, for example an engine that idles for 40 hours will have much less wear than an engine that was run at full throttle. A good way to check is to look at the Radical warrantee, if I remember correctly it specifies 40 total hours.
Thanks Dan and Charley for the input. I have sent an email to Spring Mountain for clarification, and I will likely send another to the factory. It would be useful to hear what they have to say, although I plan to use on-load hours for engine refresh scheduling based on discussions with two race teams that support the SR3. (FYI, Spring Mountain has told me that the input shaft bearing upgrade does not increase the lifing interval of the engine.)
It does not make sense to me that the engine life is degrading significantly while it idles to warm-up temperature. My engine is well past 40 hours of run time which is one data point. At 40 hours of on-load time I expect to have about 77 run time hours on the engine. I will keep the forum updated.
At the very least, I think the owner's manual should clearly specify the on-load time lifing schedule for the engine and other components, which is why I created the thread topic.
I called the Radical engine department in the UK, and I was able to talk to I think the lead engine rebuilder as well as another engine tech. They both confirmed that the refresh schedule for the 1500cc RPE engine is 40 hours of total run time.
I had a lengthy conversation with them, so I will pass on some of the noteworthy points.
- It is not the engine idle warmup time that contributes to significant wear on the engine, but the time on the track combined with the transition after running a full power session and then cooling down. He said they have always used 40 hours total run time as their guideline for refresh schedule.
- I told them I have 31 hours on-load and 60 hours total run time. He wanted to confirm I have a 1500 and not 1340, upon which he said I have done well. He also suggested to get the engine refreshed now.
- He said the top end of the engines usually do not fail first, but the bottom end -- the transmission components usually fail before anything else, in which case it does a lot of damage to the engine, requiring a more expensive repair.
- I asked if there are any indicators that one can use to predict an imminent engine failure, and the answer is not really. Usually the bottom end will fail without warning. He did say that if there is excessive metal in the oil or shift problems, this often indicates that the engine has or will fail soon.
It is hard to argue with the factory on this, but I will probably still try to stretch my refreshes to 40 hours on-load. I only have about 8.5 hours to go on this one. I have about 600 on-power overrevs and zero off-power overrevs. I don't know how that plays into it, but certainly it would be better to not have a lot of overrevs.
If anybody else has experience they would like to share on this topic, please do. I know Dan Millsaps had an engine failure due to the input shaft bearing which happened to many engines and they have now have created an update for this issue. Engines with the updated input shaft bearing are marked with an X following the engine id number, and must use Motul 15W-60 300V oil instead of the 15w-50 oil.
As far as the spin-safe clutches, it has been discussed that they will fail quickly if one does not closely follow the break-in procedure and subsequent adjustment regimen. I burned out two prematurely due to neglect and improper break-in, however this third one has been very solid due to proper attention and adjustment.
Thanks David. Very important correction in post number 2, you wrote "The Mustang GT3, built for IMSA GT3 race series, cost about 250k in 2017. (The updated FIA GT3 2023 version from Ford will certainly be much higher -- I would guess in the 400k-500k range.)"
You wrote GT3 but that is not correct its GT4 which is drastically different in performance. Your cost figure is correct but GT4 and not GT3. I am positive of this because the first ever Mustang FIA GT3 is not coming out till 2024. GT3 cars in todays world are $650,000 - $800,000 per car new. Here is a reference mark for you on the new GT3 Corvette coming out: https://www.corvetteblogger.com/2023/02/01/corvette-z06-gt3r-price-revealed/
Basically unless its Road America GT4 cars are slower than SR3 1340 yet GT4 cars cost over double to purchase and operate. At Road America a SR3 1340 do basically the same lap time as GT4, 1340 just slightly slower. To purchase a new GT4 car you are in the $250K - $400K range depending on the manufacturer.
On the engines: The way Radical accounts for engine time is not traditional with counting hours & not miles, counting idle time etc. But they figured their system out and it works. Most manufacturers do it based on running miles. When we first joined we thought the counting of idle time was crazy as most people have that reaction but Radical is correct. We tried stretching our first one. I did a back to back chassis dyno test with another new car when I got it and the stretched/over hour'd motor had lost alot of power (down 8HP) and then it had gearbox problems right after. On the flip side I have put 2 brand new cars on chassis dyno and they ran within 3/10's of a horsepower! So radical builds an extremely equal piece. Obviously the discrepancy of old vs new was accurate to say due to being over hours because the motors are extremely equal when fresh.
I have seen this scenario a few times with customers outside our dealership. Whatever you think you're going to save by stretching the motor 10-20 hours more you will pay in rebuild cost (if you dont blow it up anyway). More items will be consumed, consumed worse etc. So what you think you saved stretching the motor, it wont be saved, plus you'll be running around down on power even if you dont realize it. I see it all the time where the motors of cars we keep in house have the motor sent the rebuild cost is $X. When I organize a motor of a customer who went way over hours its always a much higher engine rebuild. Usually to the tune of about $2,000 so about 20% more.
But point being is, bang for buck, if you are a track day, club racing or pro racing guy it is very hard to beat the value Radical offers. From all aspects such as operating cost, purchase cost, all the different arenas to use the car etc its hard to beat.
Radical New York, Servicing The North East
631-974-4379
www.GroupARacingTeam.com
@DavidF, when was your last SM refresh? 11k seems low.
My thoughts after running the SR3 for about 3.5 seasons is that the car is indeed blazing fast for the money. Moreover, the way it makes its laptime is a total thrill. Fast through the corners and slow-ish on the straights is way more fun than the other way around IMO. However, the Radical requires more maintenance and shit breaks more often than GT cars. Racing this car as a DIY effort is quite a bit of work and stress.
If you exclude the cost to buy the car, I believe running costs are only slightly cheaper for the SR3 vs a GT4 car. The GT car spends a lot more on tires, fuel, and brakes, but does not have as much random breakage or as short maintenance intervals all over the car.
When you consider racing.. at least at our club, the GT cars behave themselves a lot more than the Radical guys. You don't see nearly as many incidents and these must be factored in as well since they can be very costly too.
@DavidF, when was your last SM refresh? 11k seems low.
July 2022 with Spring Mountain Powertec America. The damage on this engine after 25 hours on-load was minimal but needed a new clutch and transmission parts. I would imagine there are many standard replacement parts, but I did not pay attention to those details.
It might be worth sending my next timed out 1500 to Radical in UK. For a while the price to ship and the lead time was unacceptably high, but I think both have reverted back to pre-pandemic levels.
What a great topic!
I'll come at it from the other side: Radicals are slow, fussy, and expensive compared to proper SCCA sports racers like, say, a Stohr WF1 or an ex-IMSA Lites car. We have a fellow in Ohio running a forced-induction Staudacher and he's posting laptimes that would put him in the front half of an LMP3 grid. He has well under $100k in the car.
That being said, Radicals have a much better and safer seating position IMO, it's often (but not always) easier to get parts, and if you want to stay in the walled garden of Bluemarble and never face a real SCCA P1/P2 car you have nothing about which to worry.
"Tires are a big variable. If you race, then you spend about $3500 on tires for the weekend. That makes the refresh cost look pretty reasonable."
My total tire budget for 11 race weekends in my P$6 has been about $3k total. That's three sets of used tires from John Berget and one new set, all Hoosier R35 or R35B. But again, I'm not in a situation where I have 17 identical cars around me and every heat cycle counts.
Having driven three different variants of factory GT4 cars plus the K-PAX McLaren GT3, I feel safe in saying that Radicals are more enjoyable to drive than all of those factory racers. Some are claustrophobic, some are uncomfortably wide and heavy, none of them know how to turn. 🙂
Are there any cost estimates on the rebuild of a 1340 engine? If the same dollar amount, its is in essence cutting the cost per hour in half for the drive train, and I wonder about consumables if the car isn't carrying as much speed. (not by a lot) but in braking effort and tire wear.
don't you guys think using this hayabusa engine really hampers what could be an amazing package? I get the appeal of high revs and noise, but if the car came with an ordinary car engine with forced induction and significantly longer times between engine rebuilds and lower maintenance cost - like the engines you get in Tatuus F4 cars - i would happily sacrifice noise and revs.
Why are the costs in the US so much more? At current rates, £2800 for tyres? Medium hankooks in the UK used for the challenge series are £1600 last time i checked. Radical quoted me £6.6k (incl. VAT) for a rebuild including upgrading the bearing - excluding any random additional problems they could find. Call it £7.5k ~ $9k
Performance
i don't think anything comes close to the SR3 1500 for £/performance, especially when bought as a second hand package like i did, at roughly half the cost of a new car.
I've just scribbled this table together looking at the benchmark times and made some quick ratios based on how much the car in each series would cost for a good used example. I'm too tired to think about how best to show what remarkable value the SR3 is for the laptime relative to other cars....i'll think about it tomorrow at work instead 😀 :
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There's no other race series in the UK that i can think of which comes close to these laptimes - other than the F1000/Formula Jedi series which can run 2-3s quicker than the SR3 but are the most unsafe looking things to have an accident in.
As for road cars - forget it! Here's an example of what is clearly a very competent driver ragging a well sorted GT3RS (previous gen) and manages a laptime 4 seconds off the SR3. Obviously slicks would make a big difference but no one i've seen at a typical track day in the UK would be sticking slicks on their Mclaren 720s 🤔. I think you'd probably need a Mclaren Senna or equivalent hypercar to beat an SR3 on road legal tyres.
If there's one thing i wish the SR3 had, it would be a regular car engine which could be easily tuned/boosted to deliver as much power as the chassis could handle and therefore more thrills - for track day goers, obviously not viable for people racing in radical series. I guess that's why there's an SR10 but i'll never be able to afford one 😪
As the RPE agent here in Eastern Canada, I can say that the processes and procedures we use come from an incredible amount of data and expert analyzing to provide the best balance.
Without going into great detail, I have added a photo showing that pushing limits beyond recommended intervals can be catastrophic even with the small bearing intact as an example. The added costs for failure compared to a routine rebuild have already been pointed out. Follow the owners manual and experience the best possible value.
don't you guys think using this hayabusa engine really hampers what could be an amazing package? I get the appeal of high revs and noise, but if the car came with an ordinary car engine with forced induction and significantly longer times between engine rebuilds and lower maintenance cost - like the engines you get in Tatuus F4 cars - i would happily sacrifice noise and revs.
I think it has been done with the SR10, but it is uncertain to me whether that has decreased overall maintenance cost. The SR3 is a good car because it is well balanced with sufficient downforce and power to weight to make it fast. If you add 300 pounds of weight, it changes the character of the car. I have not driven an SR10, but I see the difference on the race track. They are faster in the straights and a little slower in the corners.
Tatuus is building some awesome cars that are very safe, light, high power to weight, and sufficient downforce for their weight. Unfortunately there is no amateur race series for any of their cars and they don't make good HPDE track cars because an impact with a heavy car would be disasterous.
I have an SCCA Enterprises FE2 which is an open-wheel car, steel tube chassis with a Mazda MZR 2.0 engine. It has everything one could ask for in terms of performance and low maintenance cost, however it would not make a good track day car, and the race series does not offer as much track time at events as the Radical Cup series. There are several other race series that offer more track time but the expense is above what I am willing to spend.
The frequent engine rebuilds of the SR3 is an expensive annoyance, but the expense is worth overlooking because the car is excellent for racing and track day use. As Radical Motorsports says: "the Radical SR3 is the world's best selling race car for a reason."
