818R Performance Expectations?

[Bob Cowan]

I'v been thrashing my Cobra for a number of years, and I think I'v squeezed just about all I can out of her - god bless her. She's very fast, and a whole lot of fun. But she's starting to show her miles.

I'm starting to think about building a track only car. My first thought is the Superlight Nemesis. http://superlitecars.com/nemesis/ It's affordable to build and race, and has amazing performance specs. It has a LOT of bang for the buck.

The only down fall is that it's a one seat car only. I also teach, and there is a lot of value in taking a student out for a ride to show them how it's done. That's usually when the light comes on. I like taking friends for rides around the track, too. That's a memorable day for both of us.

So I started looking at the 818R. Cost to build is a little bit cheaper, but not a whole lot. I'v done a bunch of reading, but I have some unanswered questions.

- Can the 818R be built as a 2 seater with a fuel cell?

- It appears that a reliable engine can be built with about 325'ish hp. What's the top speed you can expect with an engine like this? I'm running 145-150 now, and I want to be close to that with my new car. I see the factory car hitting 135 at VIR.

[AMW1011]

Can't speak authoritatively to the fuel cell question, but I cant imagine that you can make something work. A lot of people are looking into an SR type build which is somewhere in between the S and the R. At those power levels a modified WRX (the donor) is aero limited to around 160 mph. The lack of weight wont really help the top speed much, but depending on the aerodynamics an 818 should be able to blow past that fairly easily. You could get a built gearbox for racing and put more optimized ratios in it as the stock 5 speed really drags in 5th which I'm sure doesn't help. An 818 with that amount of power should hit 150mph. Admittedly, there is absolutely no replacement for lightness, so I would imagine that Superlite to perform better on a track than an equivalently priced 818, but the 818 will be a lot more livable. Then again for the ~$30k one of those would cost to build you could be pushing 400whp with built gears fairly easily.

[longislandwrx]

The diagonal crossbar has been removed from the production R. No issues installing a second seat. A fuel cell will be up to you though, either a custom one in the factory location or a smaller one in the front of the car where the battery goes.

[SixStar]

On thing to keep in mind are the transmissions. I've tossed two so far with only 260 awhp and 260 ft/lbs. Even managed to trash a RalliSpec RA box. The 5MT is pretty weak compared to the 6MT (which we can't use). Custom gear sets are a plus but are pricey. Also, I'm not sure where most people are getting these insane numbers from, a stock WRX makes 160ish AWHP. It take a fair amount of parts and tuning to break 200 to the wheels. Even a stage 2 STI only makes about 260hp/285tqs at the wheels. I know there's a lot less driveline loss on the 818 setup but not that much.

[bbjones121]

Get a Legacy gt tranny. Oh wait don't...I want another.

[shinn497]

Also don't forget the 2wd conversion and more free flowing exhaust (due to the decreased length).

This should net you some hp gains that will translate to a higher top speed over a comparable wrx.

Speaking of aero, I'm also pretty sure that the 818 has a lower cross section and therefore less air resistance. Of course how much of an effect this will have is yet to be determined.

[AMW1011]

On thing to keep in mind are the transmissions. I've tossed two so far with only 260 awhp and 260 ft/lbs. Even managed to trash a RalliSpec RA box. The 5MT is pretty weak compared to the 6MT (which we can't use). Custom gear sets are a plus but are pricey. Also, I'm not sure where most people are getting these insane numbers from, a stock WRX makes 160ish AWHP. It take a fair amount of parts and tuning to break 200 to the wheels. Even a stage 2 STI only makes about 260hp/285tqs at the wheels. I know there's a lot less driveline loss on the 818 setup but not that much.

I don't think he specified 325whp, I assumed he was refering to BHP which would be about 288RWHP or 270AWHP which is fairly easy to obtain. Your point about the 5 speeds is valid, though I rarely see people have that much trouble. He is also comparing it to another kit that starts at around $30k completed so he should have plenty of room for a reliable ~300RWHP and still change left.

[Slatt]

Even managed to trash a RalliSpec RA box.

I dunno that there is any good way to answer my question but, eh, are you hard on trannys? I don't want to re-open the whole 5MT tranny debate so let's just assume the 818 will be inherently easier on a tranny than a WRX is. I'm asking because some of my build plans are based on the assumption that the RalliSpec RA gears will last awhile. We all intend to use our 818s differently. Mine will be like a daily driver with at most 300 miles/year of track/auto cross/hard use. My experience with the 5MT is with an ESP prepped WRX which was within a few microns of grenading when it was rebuilt at 20K miles. Since then I've learned to be nicer to my baby and tripled those miles without troubles. So, I guess what I'm really asking is whether or not the RalliSpec RA gear set is stronger than an OEM gear set?

One thing is for sure: if you plug a used 5MT into your 818 kit without inspecting / rebuilding it you cannot even guess how long it will last.

[Bob Cowan]

From reading and talking with my local speed shop (that I trust explicitly), building a dead on reliable 325'ish hp engine is fairly easy to do. That's crank HP, not RWHP. The big "trick", is to go easy on the boost - don't be greedy. Like any other engine, use quality components

One of the big costs in upgrading the power levels is retuning the EFI. I might consider using a Megasquirt EFI, and solve a few problems all at once. Stand alone EFI, complete control and tuning of the EFI, complete turbo, boost, and wastegate control, and data logging.

Building a reliable transmission can also be done, but it certainly is not cheap. It is about twice the cost of a TKO! Why? But you can also tailor the gears to your liking - especially 3, 4, and 5. But $2,500 for a pair of gears? Yikes! One pair of gears for almost the cost of an entire TKO? There must be a better option somewhere.

I plan on running the car on E-85. Keeping it cool on a hot track is pretty important. The Cobra runs so much better on E-85 than it ever did on Sunoco 110 - and it saves big bux.

Snow Performance methanol injection before the intercooler isn't out of the question, either. That would all depend on the intake charge temps.

So, here's the question. 325 crank hp + 0.93 5th gear + 818R.... does that = 150 mph on the average club track?

[bobzdar]

From reading and talking with my local speed shop (that I trust explicitly), building a dead on reliable 325'ish hp engine is fairly easy to do. That's crank HP, not RWHP. The big "trick", is to go easy on the boost - don't be greedy. Like any other engine, use quality components

One of the big costs in upgrading the power levels is retuning the EFI. I might consider using a Megasquirt EFI, and solve a few problems all at once. Stand alone EFI, complete control and tuning of the EFI, complete turbo, boost, and wastegate control, and data logging.

Building a reliable transmission can also be done, but it certainly is not cheap. It is about twice the cost of a TKO! Why? But you can also tailor the gears to your liking - especially 3, 4, and 5. But $2,500 for a pair of gears? Yikes! One pair of gears for almost the cost of an entire TKO? There must be a better option somewhere.

I plan on running the car on E-85. Keeping it cool on a hot track is pretty important. The Cobra runs so much better on E-85 than it ever did on Sunoco 110 - and it saves big bux.

Snow Performance methanol injection before the intercooler isn't out of the question, either. That would all depend on the intake charge temps.

So, here's the question. 325 crank hp + 0.93 5th gear + 818R.... does that = 150 mph on the average club track?

Not based on the 818R testing at VIR. That back straight out of oak tree is quite long and I think I saw a peak of 137mph on their car making 340hp, and it was not gaining speed very quickly at all at that point, so you might get 140mph out of it. I think it has too much drag to get near 150mph on any normal track with that much power unless they were having some engine trouble and it wasn't putting out the full 340hp. Fwiw, my f355 was pulling 140-145mph as I crested the hill on south course (where the 818r was doing about 130mph), but that's where I had to slam the brakes on. That's a solid 10-15mph faster than the 818r at that point and my car has (claimed) 380hp and weighs 3050lbs. It has no wings or doodads other than the stock rear diffuser, though, so I think the 818r in stock form has a lot of drag (but also way more downforce). Such is the nature of a track car vs. a street car, though. You won't be getting super high speeds out of it due to the aero, but corners are where the time is.

[Jim Schenck]

You can't really base speed from the VIR track event since the car was so compromised by not having third gear. The challenge cars hit between 143-145 on that straight (and 150 in the draft) and they do not pull as hard as the 818R at higher speeds. (according to the data we took) I think 150 is a reasonable guess as to what the car would have done if it had been 100%, but also VIR is a pretty long straight compared to most so I would say that is about the top speed you would see at similar size tracks (Road Atlanta, Summit Point, Sebring, etc..) but at many of the shorter tracks 135-140 is more likely.

[Mechie3]

From reading and talking with my local speed shop (that I trust explicitly), building a dead on reliable 325'ish hp engine is fairly easy to do. That's crank HP, not RWHP. The big "trick", is to go easy on the boost - don't be greedy. Like any other engine, use quality components

One of the big costs in upgrading the power levels is retuning the EFI. I might consider using a Megasquirt EFI, and solve a few problems all at once. Stand alone EFI, complete control and tuning of the EFI, complete turbo, boost, and wastegate control, and data logging.


Has your speed shop done Subaru's before? I only ask because their are some quirks to them if you're doing a ground up rebuild that the average V8 shop can't do/doesn't do/does wrong.

325hp is cake on a 2.5l motor. My stock block, stock head, stock turbo 2006 WRX made 312hp and 451tq (crank numbers). All of engine failures were attributed to non power related issues (ripped o-ring, blown headgasket on junkyard motor). All failures occured during daily driving, never during a race. In it's last configuration, it lasted 22k miles/2years of daily redlining on the way to work before the car's demise.

EFI isn't expensive at those levels either. You can get an open source tune for a few hundred dollars, or buy a Cobb AP (they just came out witha new V3, so the V2's will soon be cheaper if you don't want the V3 features). The AP is around $600, a protune would be another $300ish.

[bobzdar]

You can't really base speed from the VIR track event since the car was so compromised by not having third gear. The challenge cars hit between 143-145 on that straight (and 150 in the draft) and they do not pull as hard as the 818R at higher speeds. (according to the data we took) I think 150 is a reasonable guess as to what the car would have done if it had been 100%, but also VIR is a pretty long straight compared to most so I would say that is about the top speed you would see at similar size tracks (Road Atlanta, Summit Point, Sebring, etc..) but at many of the shorter tracks 135-140 is more likely.

I imagine the challenge cars pull harder at lower speed. The comment was more compared to my car where I have a much lower power/weight ratio but was seeing 10-15mph more in the same area, presumably due to drag differences. It wasn't a knock on the car, as for example the 818R was a solid 10mph faster in the high speed left hander before oak tree than my car, presumably due to that aero and sticky tires and would absolutely eat up a street car in the climbing esses. Hopefully you guys go back sometime soon with a good trans....

[Jim Schenck]

Didn't take it as a knock at all, just in talking to John the backstraight was one of the places he was the most frustrated by the lack of third. The jump from 2nd to 4th was just to big and was exaggerated by the larger turbo. I think with just a functioning third we would have seen 150 based on how hard the car pulls from 110 on when compared to the challenge cars but won't know for sure until our next trip down there with the car.

[flynntuna]

Will it be possible to do a postmortem on the tranny to determine what caused the premature death of that 3rd gear? There was a thread early on which linked to a company that developed an aftermarket brace that prevented the tranny case from flexing. I don't remember the details, I'll go back to find it.

[Bob Cowan]

Thanx, Jim ( and all). That's just the kind of information I was looking for.

The Superlight car looks pretty exciting to me. But Fran is talking about shelving the exo cars, and focusing on other models.

The 818 looks like my #1 option; it should meet all my performance and fun goals for a minimal investment. I just don't see a better bang for the buck anywhere on the planet. I think you could build a Corvette killer for under $25K. :)

[Ironhydroxide]

Will it be possible to do a postmortem on the tranny to determine what caused the premature death of that 3rd gear? There was a thread early on which linked to a company that developed an aftermarket brace that prevented the tranny case from flexing. I don't remember the details, I'll go back to find it.



transmissions are difficult to "postmortem" because of the inherrent damage caused by the failed teeth. it must've completely stripped a gear (i'm Guessing the input shaft gear) for the car not to be very lurchy.

i've personally seen teeth break off previous to full gear failure, where it looks as if the tooth just popped off.. wasn't ground, or bent, just found a flaw in the casting and popped. I'm guessing this happened to one of the gears for 3rd, and once the directly following tooth got enough beating from the extra torque it failed... Once 2 consecutive teeth were missing, the entire gear spun through.

[THE ITALIAN]

Thanx, Jim ( and all). That's just the kind of information I was looking for.

The Superlight car looks pretty exciting to me. But Fran is talking about shelving the exo cars, and focusing on other models.

The 818 looks like my #1 option; it should meet all my performance and fun goals for a minimal investment. I just don't see a better bang for the buck anywhere on the planet. I think you could build a Corvette killer for under $25K. :)
I looked at that superlite too, it is intriguing, a little "can-amish" for a street/track combo, but like they say, Superlite for sure. I won't build another car w/o side impact protection-period. everyone says "safer than a motorcycle" True , but safety first as I age.
$25 grand can be had, from what I have seen so far, "it's going higher for me" and this tranny talk,,, I do think it needs a beef job. I also questioned earlier, about the balance of the transmission, by the 818 removing Torque from the tail shaft, it was designed by Subaru to have this torque on the end shaft.
The argument is, the 818 is lighter than the Subaru, so therefore no problem. I think there may be an issue here, I'm no engineer, but I do think there could be and from what I have read, 3rd gear is a weak link.

[riptide motorsport]

Plus..............its just plain FAST lookin'!!!!



Thanx, Jim ( and all). That's just the kind of information I was looking for.

The Superlight car looks pretty exciting to me. But Fran is talking about shelving the exo cars, and focusing on other models.

The 818 looks like my #1 option; it should meet all my performance and fun goals for a minimal investment. I just don't see a better bang for the buck anywhere on the planet. I think you could build a Corvette killer for under $25K. :)