Planning stage on my home built autocrosser ....

Look at FSAE powertrains, you'll be building something very similar to an FSAE car, much like what's pictured on the front of the book Woody recommended. They usually keep the bike gearbox and run the chain to a custom rear end.

It probably depends on what you're really looking for. If you just want to race for cheap, an old Formula V is hard to beat. Another option is a F500 or F440, assuming you can live with the "leaf blower on steroids" aspect. Those can also be found used for fairly cheap and generally have lower operating costs than a FV. Either will definitely less than you'll spend building a car from scratch.

I have been working on my own B-Mod for a few years. See below for an old picture that doesn't represent its current state.

A lot of good advise are given already in this thread, but here are my experiences:

1 - Start by reading the rules that you want to run in. Making changes once a project as started can be the kiss of death. This is actually the second frame I built. And there are still some aspects I would change.

2 - Identify your goals and limits and stick to them. I wanted my project to be fun, safe, cheap and fast. In that order. So I made compromises accordingly. And I try to always stick to it. Once done, I will probably be under challenge budget

3 - While help is always welcome, don't count on it to move forward. For example, if you need to rely on someone else to weld, you will never finish. So be prepared to acquire a lot of different skills, or don't even start.

4 - Don't let analysis paralysis take over and don't try to be perfect. Heck OEM's send cars to market with a bunch of unresolved issues, so if you think your first project will be perfect, think again.

Concerning your project in itself:

1 - DOM and ERW tubing frame. 4130 is a lot of headache and expenses for almost no advantages.
2 - Bike engine. Check the book already mentionned in this thread. It's good. I'm using an RX1 snowmobile engine in mine.
3 - Stick with as much off-the-shelf stuff as you can. I made my own front uprights, and it is a pain. I would compromise the geometry for an OEM part if I were to start over.

And good luck!

For whatever it's worth, we discussed a lot of this back in the Abarth SP 1000 thread. Many links to parts sources and engine ideas.

I'll admit, the LOGIC behind a bike motor is very strong, and I can see all the advantages. But, on the emotional side, I just can't clear that hurdle right now. I just kept going back to car engines and different ways I could make them work the way I want to. Maybe it's the side, or the sound, or just the overall look of all the Formula SAE's and F600's and such, I just can't get into the idea, and if I can't get into it emotionally, the project ain't gonna make much headway.

Still going to check out those threads and books though, and that Abarth thread looked like it could have been epic.

I'm going to stick with finding a car engine/transmission combo that I think is going to hit my target numbers, and if I go over on the weight than I go over on weight. And to hit that new 1250lb or so target, and around 125hp, I may have found my combo. 4AGE mounted longitudinal, mated to a VW type 2 transaxle, flipped around ALA Formula VEE with the engine in front of the transaxle. So think of it like a ghetto Formula VeeLantic? Apparently it's a fairly easy combo to make and pops up sometimes in sandrails and beetles, just takes an adapter plate and modified VW flywheel.

This'll also let me start taking some actual measurements of things as I have a spare 4AGE in the garage and VW transmission measurements are easy to find. Should also push the engine weight, and myself, further forward to help improve the weight distribution.

I think your 1000 lb goal is unrealistic since you are already dismissing stuff like 4130 alloys for the frame and bike engines for the power; because it is too hard or not your thing. 1000 lb race cars require that you drink a lot of strange, difficult and expensive kool-aid like drilled titanium fasteners, carbon fiber brackets and light beer, because they save a fraction of a gram of weight times however many fasteners, beers and brackets you have.

If it were not so long in the tooth I would suggest the Suzuki Swift engine as a great light weight power source. Bolts to a samurai gearbox.

I also agree that you better treat this as a welding school. No "friend who can weld" is going to survive the hours needed to get this king of a project done on a volunteer basis. I would embrace the opportunity; if you came out of this project proficient in tig welding chromemoly, that alone would be worth it.

1500 lbs is a realistic goal in my mind if you stick to your plan.

NOHOME wrote: I think your 1000 lb goal is unrealistic since you are already dismissing stuff like 4130 alloys for the frame and bike engines for the power; because it is too hard or not your thing. 1000 lb race cars require that you drink a lot of strange, difficult and expensive kool-aid like drilled titanium fasteners, carbon fiber brackets and light beer, because they save a fraction of a gram of weight times however many fasteners, beers and brackets you have. If it were not so long in the tooth I would suggest the Suzuki Swift engine as a great light weight power source. Bolts to a samurai gearbox. I also agree that you better treat this as a welding school. No "friend who can weld" is going to survive the hours needed to get this king of a project done on a volunteer basis. I would embrace the opportunity; if you came out of this project proficient in tig welding chromemoly, that alone would be worth it. 1500 lbs is a realistic goal in my mind if you stick to your plan.

I already did bump my weight limit for the car up to 1250, the 1000lbs just wouldn't happen with a water cooled car engine. But don't forget that I'm not trying to go as light as possible, I'm trying to go as close to 11:1 lbs/hp with driver, without going too light/too powerful. Otherwise I'll have to ballast to stay inside TT1 and not get bumped to TT2.

As to using 4130 vs 1018, I just don't see a huge advantage for the additional work and cost. For the cage structure, which is going to be a significant portion of the chassis, I can't go any smaller than 1.375x.095 or 1.5x.080, regardless of material. It's not like other rules sets that let you go a size smaller for 4130. I'm also paranoid that eventually the 4130 might get banned for chassis and cage construction within NASA, they already banned it for rally cars. So my plan was to use 1.5 x .080 DOM for the majority of the structure.

I'm figuring about 175lbs for the chassis, 600lbs engine/transmission, 100lbs wheels/tires, leaving me 375lbs for the rest of the car minus the driver.

You're right though that I'll be doing a lot of the welding myself in all of this. Just that I'd rather have somebody better than me handle the critical spots in the structure, while I get up to speed again. Been a while since I've done significant welding.

-Hans

I understand being under-weight and having to add ballast isn't necessarily a bad thing. It allows you to place weight where it can best help the balance of the car.

As mentioned in the SP 1000 thread (yes - a shame that didn't work out as hoped), my eventual goal is a street legal B-Mod car that I can drive to local events. Unfortunately, many existing projects ahead of that one.

Ian F wrote: I understand being under-weight and having to add ballast isn't necessarily a bad thing. It allows you to place weight where it can best help the balance of the car. As mentioned in the SP 1000 thread (yes - a shame that didn't work out as hoped), my eventual goal is a street legal B-Mod car that I can drive to local events. Unfortunately, many existing projects ahead of that one.

That would be cool to see, a street legal B-Mod. I know what you mean about too many projects, still haven't gotten back to my '68 Airstream yet.

And yeah ballast can be good to a point, as it lets you adjust weight distribution and keep the CG low. But it does hit a point of diminishing return where you could have used the weight to do other things.

-Hans

Starting to pull some dimensions together on the 4AGE/VW combo to see how things may line up, and start nailing down at least a wheelbase and track width to shoot for. Going to stick with the 1.6:1 ratio of wheelbase to track. Did up a quickie sketch and it looks like it's really going to push me forward with the longitudinal engine layout, which is what I was hoping to see.

Starting to get a vision in my head of the general chassis layout, essentially a 4 or 6 stringer, along the lines of a fairly recent Formula Vee, but with more support for the drivetrain area behind the driver.

-Hans

My bike engine builds(autox'r and ice racer) is on here somewhere,youtube vids under the same kevlarcorolla.Knowing what I know I doubt that unless your building aluminum uprights and other serious weight saving tricks you'll struggle to get anywhere close to 1250lbs with a car drivetrain,especially a cast block 4ag,honestly there's lots of better options then those.I say that having built my own supercharged 20v and turbo'd 16v 4ag's for my AE86.

You really do want a bike engine(or a sled engine,those can present further complications though),gear it steep so you don't use 1st at all and take advantage of the close ratios from 2nd and up.

In reply to hhaase:

Be sure to check the rules regarding the wheelbase and driver position. I'm near certain the front axle line has to be ahead of the pedal box area to comply with GC requirements. A number of old F-Mod/F440 cars have been relegated to autocross only because of this. I know you are looking more at NASA rules, but building with SCCA rules in mind as well will greatly increase future resale ease, if needed.

4age engine weight is very close to that of an air cooled vw. Formula Vee, Super Vee, Formula First cars all hit the scales in the 1000lb or less range. Formula Atlantic, with all the aero package and everything, is right around 1250lbs with a 4age. The VW based series are not high dollar events running expensive and exotic materials. Numbers so far are still telling me I won't have a problem hitting the weight I want. If anything, the more weights I plug in, the better it looks. Engine and Transmission combo looks like it'll come in close to 400-450 including externals such as radiator and oil cooler, that's 150lbs less than originally guessed at.

Stock 4ag is 113 hp and over 35 yrs old in design.Good luck affording a formula atlantic version.

I have one in my basement with the typical rod knock on #4,otherwise in good condition.If you were closer you could come and pick it up for free.

Stock R1 is 150hp and 150lbs with all fluids AND transmission along with a very compact 2'x2'x2' cube for packaging.

I'd go with a Kawasaki ZX1200 or better yet the ZX1400,both will weigh around 180'ish lbs complete and only a slightly larger area.

Also you started this thread with the title auto'x build but are talking about track now and not a word about autox,of course you can build one buggy to use for both but you need to pick a priority imho.

kevlarcorolla wrote: Stock 4ag is 113 hp and over 35 yrs old in design.Good luck affording a formula atlantic version. I have one in my basement with the typical rod knock on #4,otherwise in good condition.If you were closer you could come and pick it up for free. Stock R1 is 150hp and 150lbs with all fluids AND transmission along with a very compact 2'x2'x2' cube for packaging. I'd go with a Kawasaki ZX1200 or better yet the ZX1400,both will weigh around 180'ish lbs complete and only a slightly larger area. Also you started this thread with the title auto'x build but are talking about track now and not a word about autox,of course you can build one buggy to use for both but you need to pick a priority imho.

Priority is NASA TT1, which is their auto cross/time trial rule set. That's the goal. 150lb and 150hp will probably bump me into TTU, which isn't where I want to go.

I'm not looking at sourcing an FA engine, just using it as a comparison to show my weights aren't unreasonable. This isn't a build where I'm looking to maximize my power to weight, I'm trying to hit a specific ratio and not go too powerful or too light. 11 lbs per hp, including driver.

I know NASA lets the Exocet run (sort of) but other than that they seem to dislike open wheel cars. The fast TTU guys are seeing over 170mph on the tracks in Texas. I can't quite imagine that speed without some serious thought to a body and aero.

mazdeuce wrote: I know NASA lets the Exocet run (sort of) but other than that they seem to dislike open wheel cars. The fast TTU guys are seeing over 170mph on the tracks in Texas. I can't quite imagine that speed without some serious thought to a body and aero.

Already spoke with the local group, won't be an issue. But yeah that's why I don't want to run TTU. Just too much.

Will need to either use fenders or a full body. Haven't settled on which yet, probably some kind of hybrid, but can't go fully open wheel.

hhaase wrote: Starting to pull some dimensions together on the 4AGE/VW combo to see how things may line up, and start nailing down at least a wheelbase and track width to shoot for. Going to stick with the 1.6:1 ratio of wheelbase to track. -Hans

Interesting. I see that being good for autocross, might be a little twitchy on a big open track with a heavy braking zone... based on my experience with a miata (1.6 WB/T ratio). But, some aero might help settle that down, and the mid-rear engine layout will help the brakes do more work, which will help with stability.

I think you've got a pretty good shot at meeting your weight goal. I wonder if some of this isn't due to most of the designs people are used to evaluating being two-place vs. single?

In reply to sleepyhead:

Very possible, or may also be that this is more often seen in SCCA, where the rules really shove you into certain design philosophies.

As far as weight distribution, Don't forget too that I'll be doing the engine longitudinal, Not transverse. So that's going to push weight forward, plus I'll be able to keep the Cg low. Aero I'll have to develop later on once I know more as far as body dimensions.

First off, I find this idea interesting, will be great to see how it develops and shapes up.

A 125hp 4AGE will be quite a bit heavier than a bike engine, but also with more torque and potentially a lot longer service life.

My frame of reference for weight is purely anecdotal, and is based on a strong interest in the 4AGE and twenty years of lurking and dreaming on various Seven/Lorus/Locost forums and mailing lists. I realize you aren't building a Seven, but it is closer to what you are talking about than most other street cars, and gives us some data that isn't a formula car.

It seems that building a 1000 pound Seven is possible, but not easy, and typically involves a bike engine, massive obsession with weight, and may not be street legal in terms of lights, fenders, etc. The AE86-based Locost builds that are focused on weight reduction (think lightweight wheels, aluminum brake calipers, small alternator, minimal lights, fixed "seats," and no convertible top/side curtains) seem to be in your new target weight ballpark; 1250-1300 pounds or so. The 4AGE builds focused on getting roadworthy cheaply and easily (stock iron hubs and calipers, glass windshield with wipers, steel floor, big mufflers, maybe extra bracing in the chassis, maybe a heater, adjustable seats, etc) seem to end up in a 1450-1650 pound weight ballpark.

I think 1250 is a reasonable goal for a mild steel frame with 4AGE power, but to reach it you will probably have to keep an eye on weight throughout the build.

Looking forward to seeing where the 4AGE plus VW exercise leads!

I'd scanned too quickly previously and only just now noticed you don't like the sound of an inline 4 bike engine??.Sounds like a reason to ban around here.

I'm curious about your design targets,if you only have a lbs per hp target why build using a heavy/low power drivetrain?.

Also reconsider the vw transaxle deal,simply use a transverse layout to keep your overall and wheelbase short.Every inch of length is more material adding cost and weight,you'd mentioned adding ballast as diminishing returns.I don't understand that,build it light and add ballast where best suited to meet your target is a time proven effective method.

Target a max of 90" wheelbase and very very minimal overhangs to the body(I'd prefer max of 85" but that's probably tough to meet with a car engine even transverse mounted)and go from there.65% rear weight bias is a decent starting point,easily adjusted with ballast to meet your target weight if you get it light enough.

Nohomes suggestion of a 13B Suzuki swift engine is a good one,but use the fwd transmission.The engine is light,compact and tough as nails and cams,header and tune is about 120hp with 8500rpm for a ceiling.

Lots of good engine and transmission choices from Honda,some with oem lsd trans options for a major plus.Toyota 1zz is ok I guess(you'd mentioned the 2zz,too much hp though?),gm has the LE5 for a cheap option(not that compact and tall though).

You came here for advice,doesn't sound like your that open to it though but I'll watch and see what you come up with for sure.

Have you started measuring overall length of all the components you need to fit within the wheelbase? Being able to put the transmission between the driver and passenger makes a longitudinal setup much easier to fit in a 90 inch wheelbase. You can put a longitudinal mid engine style transmission but then you need to deal with the tail of the transmission sticking out beyond the rear suspension.

MrJoshua wrote: Have you started measuring overall length of all the components you need to fit within the wheelbase? Being able to put the transmission between the driver and passenger makes a longitudinal setup much easier to fit in a 90 inch wheelbase. You can put a longitudinal mid engine style transmission but then you need to deal with the tail of the transmission sticking out beyond the rear suspension.

Started doing those measurements a couple days ago, and you are spot on that 90" isn't going to work out with a single seater. It pushes the occupant too far forward. Would have worked if I kept a transverse engine but the weight distribution in that case would be way too rear biased and too tall. So I've opted to extend to 105". This will let me keep the engine longitudinal and sink it down between the lower pair of stringers to keep the CG low. Wish that there were more older Subarus around here, a boxer would be nice.

No matter what I do with the vw box, it's going to hang out behind the rear suspension by a fixed amount. Shouldn't be too terrible though for overhanging weight and I'd need to build up bodywork in that area anyway aerodynamically. If I can find an 091 mid-shift box though it's a few inches shorter due to the shifter location.

As I said earlier, regarding engines, a lot of it comes down to ease of sourcing. The northern plains near me just doesn't have much by way of sport bikes and imports. I'd be dependent on eBay and longshot luck to find anything. Toyota and older VW are the exception it seems. Lots of old beetles and busses, lots of Toyota. I have tried looking for some of the suggested engines but they just haven't been available or the condition is highly suspect. It's the one area that a wrong decision could bog the whole thing down if I need to spend too much time or money tracking down parts that aren't easily accessible in my region. And if it stalls for long enough to kill my motivation, it'll die as a project. That's one huuuuuge reason I'm planning around the 4AG.... I have one. Then if I decide to move up a class it is dimensionally similar enough to the ZZ series that the change would be fairly straightforward and reasonably easy to source forms.

I know I may be being a bit harsh on my decision on bike motors, but I just know myself too well. I really want to do this build, and I really want to see it through. So in this case it means making a less than optimal decision in order to maintain my emotional side.

kevlarcorolla wrote: You'd mentioned adding ballast as diminishing returns.I don't understand that,build it light and add ballast where best suited to meet your target is a time proven effective method.

Actually I'm not against using weight to tailor the car to where I want it, just that if I'm adding weight I'd rather use things that are useful as opposed to just slugs of lead. I'd prefer to add weight via a fire system, accu-sump, telemetry components, battery, things like that.

I like the 4age/VW idea. Your power goals are low and car stuff should be rugged in your application. I think the 150hp weight goals are achievable.