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PostPosted: February 1, 2018, 6:54 pm 
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Vudufl wrote:
TLDR question: all other things being equal, is the additional 145 lbs in drivetrain weight (still in the same mid-engine location) worth the 50 + hp and the additional 110 lb-ft or torque?
Getting 27.5% more power, in exchange for something like 8% more total weight and maybe a 2.5% weight distribution shift to the rear?...I'm pretty confident that a stopwatch would say yes, that is absolutely worth it. Then again, if not building a competitive racecar, how important is the opinion of a stopwatch?

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PostPosted: February 1, 2018, 7:57 pm 
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We live in the golden era of horsepower, probably the last great era of actually driving a car. Having said that, HP is overrated.

Weight always has been the enemy of speed. Aero is what allowed cars of the same HP to go a lot faster too.

And in Chapman's time as now, when you add HP you end up adding weight to handle the extra HP.

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PostPosted: February 1, 2018, 8:54 pm 
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Marcus - the front engine plan I have been working on incorporates a 3” stretch to the stock 80.157” wheelbase (length added behind front wheels). IMHO that’s about the max I can add without it looking goofy or really being noticeable to the average eye. The stretch helps a little with pedal placement and gives more radiator room.

Lonnie - I like your analytical approach. The building of a custom performance car, especially one that is fabricated from a wide variety of component sources, is usually a symphony of compromises. Listing out requirements ahead of time and using that as a shopping guide of sorts is a good idea.

WelderLee - yeah, I was a bit surprised by the prices I was finding for the K20 engine/trans/ECU combo but that $4400 price seemed pretty consistent for an engine with less than 75k miles. I’ve been scouting out some running donor vehicles figuring that I don’t really care about something needing bodywork or paint...most of it would go to the scrapyard anyhow. The benefit is being able able to drive the engine and sort out any issues before tear down. Bonus: letting my teenage son use it as his first car for 6 months or so!

KB58 - I’m not sure if the high price of the K20 may be a regional issue but I do know that for whatever reason the K24 seems to avg around $1600 for engine and trans...nearly 3x the K20.

Justin - I’m not sure how much the additional weight would potentially upset the handling and although the stopwatch doesn’t lie, if the handling of the car leaves you nervous about pushing the limits, the additional power might be a moot point. I have no idea at this point (hence my post).

Tim - I’m not in the market for the kind of horsepower required to make the Mini’s brick-like aero qualities a non-issue :lol: I am planning a stiff chassis and that will add some weight but the handling benefits and the “feel” make it a good trade off, I think.


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PostPosted: February 1, 2018, 9:57 pm 
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Vudufl wrote:
Tim - I’m not in the market for the kind of horsepower required to make the Mini’s brick-like aero qualities a non-issue :lol: I am planning a stiff chassis and that will add some weight but the handling benefits and the “feel” make it a good trade off, I think.


Good. The original Seven was a lot lighter, but if you look at the frame on the thing, you'll notice a lot less of it. I think that if I posted a "look at my frame and comment" post with that original frame there are many who'd tell me that it wasn't a good idea. And when I see vintage racing events I can't help but wonder where they attach the roll cage that is strong enough to be effective.

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PostPosted: February 1, 2018, 10:08 pm 
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geek49203 wrote:
Weight always has been the enemy of speed. Aero is what allowed cars of the same HP to go a lot faster too.

Drag has always been the enemy of speed. Weight is more the passive aggressive coworker of speed.

Lighter is better only holds true up to a point.



Vudufl wrote:
Justin - I’m not sure how much the additional weight would potentially upset the handling and although the stopwatch doesn’t lie, if the handling of the car leaves you nervous about pushing the limits, the additional power might be a moot point. I have no idea at this point (hence my post).
You're building an 80" wheelbase mid engine car, and you're worried you'll be nervous about pushing the limits? Yeah, I would be too. However, I'd be more concerned with taming the short wheelbase and low moment of inertia than the weight distribution itself. Cars with everything from a noticeable front weight bias to a heavy rear weight bias have been set up to handle great. Kurt's car has a further rear weight bias than a 'treacherous' handling early 911, but due to what the world has learned about vehicle dynamics since then even at a DIY level, it is apparently by no means a widow-maker. Properly setup and tuned for each, I doubt mortal enthusiast drivers would even be able to tell much difference in a 2.5% weight distribution shift without driving it back-to-back...And it certainly won't be the difference between mild mannered and trying to kill you.

Consider that the short wheelbase on your car will also contribute significantly towards moving the weight distribution further forward than Kurt's Midlana.

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PostPosted: February 2, 2018, 10:59 pm 
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Hugely important question: Where do you want the engine to make power? (and sound, and vibes)

Five-ish main camps:

1. big torque down low, say <4K RPM - usually big displacement and heavy
2. big power up top, say >6K RPM - some people love, some hate
3. Strong mid-range, 4-6K RPM - never going to make remarkable numbers
4. Boosted for torque, (boost onset <2500RPM even in low gears, turbine choked off at 5-6K RPM - most modern OEM boosted engines)
5. Boosted for power (boost onset at 4K RPM, maybe more in low gears, Absolutely huge HP numbers 6-8K)

I'm a #3 person, love to listen to a NA engine 'come on cam' as the revs climb but I don't like feeling like I need to rev until it blows up to make the car go. I also could care less what the dyno peak numbers show if it feels good to drive.

Used to love the intoxicating technology of turbos, owned a bunch (big power and factory variations), then grew up and realized I personally think they kind of suck to actually drive relative to NA or even supercharged (gasp!) engines.

I think these are emotional cars more than anything, think long and hard about where and how you personally want to *feel* the engine work well, you can't have them all.

Long way of saying I'd pick the V6!

Alex


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PostPosted: February 3, 2018, 3:21 pm 
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Quote:
You're building an 80" wheelbase mid engine car, and you're worried you'll be nervous about pushing the limits?


I've been on the fence about saying something here, but I think you should be pretty scared. Someone I know spent months in hospital with a broken back after a road racing accident in a mini and another person that was killed when he spun his LeCar. The fellow in the Lecar actually didn't hit anything, just spinning it killed him.

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PostPosted: February 3, 2018, 4:32 pm 
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As I recall, my mid-engine Mini had a weight distribution of 59R/49F, which isn't bad, but yeah, an 80-in wheelbase makes it very quick to change directions if you aren't on the ball. At Streets of Willow Springs I had a passenger hit his head on the side window because he didn't expect it to corner so quick. He was the same guy who later said the chassis "needed" more power than the 190whp Prelude engine provided.

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Last edited by KB58 on February 3, 2018, 8:36 pm, edited 1 time in total.

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PostPosted: February 3, 2018, 7:13 pm 
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I had the same decision to make when designing the Bauhaus. I was comparing the two engines from the accord. BIL had the K24 auto, I have the 6-speed J engine in my accord. I LOVE that v6. It is smooth, revs well, pulls hard and was the perfect upgrade from my Eagle Talon 4 cyl turbo.

But while the engine is AWESOME, the 6speed manual sucks. I had the first one replaced because it wouldn't go into 3rd without shifting very slowly or double clutching. It doesn't need 6 gears, so on the street it is just annoying, not unlivable. Now, both 3rd and 4th are balking. I decided I hated the trans more than I love the engine.

Alternatives? With few (maybe no?) exceptions, all of the Toyota transverse transmissions all fit all of the Toyota 4 and 6 cylinder engines. The very light s-series transaxles can handle 200-ish hp and maybe more, but the heavier e-series can safely handle upwards of 800hp. There are 3 v6 options, the best being the 3.5 liter 2GR-FE, which puts out 300hp to the wheels with headers, an intake and a revised rev limiter. Box stock is 270bhp. Longevity is good too. My wife's Camry v6 has 250k miles and is still running barely worse than new. This is what the MR2 guys are all dropping in their cars, so the swap info you will need is well sorted.

If you go 4cyl, it's hard to beat the K24. Going v6?, I wanted the Honda bad, but there is a Toyota in the Bauhaus.

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PostPosted: February 3, 2018, 8:59 pm 
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I'll throw a few things out there:

-you can use 250lbs of torque in a Seven. I have ~280lbs and can be planted at full throttle often (even at autoX with the car/driver not setup well yet).
-the thing is to look at the dyno charts/curves of the motors. Peak numbers mean nothing. You want torque when you need it. Keep in mind that gearing makes a difference.
-torque makes street driving more enjoyable. Never have to shift, or worry about stalling.
-100ft/lbs of torque AND more power is a huge difference in a light car.
-V6 is larger: makes centralization of mass harder.
-My old V6 doesn't feel that fast in a straight line. You floor it, get a solid initial push into the seat and then don't get a sense of acceleration. You end up looking down at the speedo and wondering if you are actually going that fast (spoiler: you are!). I think it's because there is no build up as you run through the RPM range. With the N/A VTEC motor, I don't think you will experience this though: More a note for others.

TLDR: More power/torque=better. Even with reasonable extra mass penalties, your car should still be fast enough to seriously challenge/trump your driving skill.

Cheers.

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PostPosted: February 4, 2018, 9:39 pm 
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Justin - good points. “Pushing the limits” is probably more about pushing my limits which are reached before the machine’s. I’d like to build something with fairly predictable handling despite the wheelbase...not interested in a ride that behaves well but then snaps evil in a second.

Alex - nice break down. I’m probably in camp #3 or #4. At this point I’m leaning more toward the K24 option but adding a supercharger. The decision is being driven by several things including the scarcity of good manual trans for the J series V6, the space limitations and exhaust routing.

Marcus - sanity will prevail but regardless, appreciate the voice of caution.

Omterry - I had not considered the Toyota but after you mentioned it, I did some reading. It’s an interesting option but I have not had any luck finding dimensions of the 2GR FE with trans. Would you happen to have that info along with the weight of engine and transaxle?


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PostPosted: February 5, 2018, 12:02 am 
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I have 36" long (pulleys to end of the trans) x 26" deep x 28" high. These are not micrometer accurate, but include room for e.g. exhaust tubing underneath. The MR2 guys (especially Gouky and Paul Woods on the MR2 boards) will have it more precisely, like where the bumps are and how wide the manifolds, etc., because they have shoehorned at least one into a gen 1 MR2, and into an MRSpyder :shock:

They probably also have the weights (which I won't be able to pull) and Marc (Gouky) is a really stand up guy. "Service weights" wet are published by Toyota, but who knows what accessories they include in the weight. For a real-world reference, the installed weight of the 2GR Is less than the iron block turbo 4.

End result, probably a bit heavier than the J engine, but not much, and the trans is probably 25-50lbs heavier than the useless Honda box. And the transmissions are available if not xactly free. I just got a 70k mile e153 v6 trans for for $700 including shipping. All that for an engine with more stock power, a much flatter torque curve, a bomb-proof trans and a commercially available supercharger, if stock isn't insane enough. :twisted:

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PostPosted: February 5, 2018, 12:51 pm 
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I had a very similar dilemma when I started my car. I had originally planned to use a K20 but the cost was just too much. I was looking for 200hp, light, and cheap. It came down to the mazda klze v6 and the H22. I really like the v6 sound but ended up going with the Honda. I know it's not one of your current choices but I love my H22. With a few basic mods it dynos the same power as my buddies ap1 s2000 and has 20ftlbs more torque. They are also super cheap with decent aftermarket support. I paid $650 for my donor car and sold enough other stuff off it to get my money back.


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PostPosted: February 5, 2018, 9:28 pm 
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Since the K series swaps really took off in popularity, the prices of the H22s have really been hard to beat. What’s a little harder to overcome is the 485lb weight. Love the affordability but if I’m going 4cyl, I’m going try to keep the weight down as well. Regardless, I appreciate the input.

Zac88GT wrote:
I had a very similar dilemma when I started my car. I had originally planned to use a K20 but the cost was just too much. I was looking for 200hp, light, and cheap. It came down to the mazda klze v6 and the H22. I really like the v6 sound but ended up going with the Honda. I know it's not one of your current choices but I love my H22. With a few basic mods it dynos the same power as my buddies ap1 s2000 and has 20ftlbs more torque. They are also super cheap with decent aftermarket support. I paid $650 for my donor car and sold enough other stuff off it to get my money back.


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PostPosted: February 6, 2018, 10:32 am 
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Vudufl wrote:
Since the K series swaps really took off in popularity, the prices of the H22s have really been hard to beat. What’s a little harder to overcome is the 485lb weight. Love the affordability but if I’m going 4cyl, I’m going try to keep the weight down as well. Regardless, I appreciate the input.


KB58 Posted in here viewtopic.php?f=4&t=4299

KB58 wrote:
(Entire here means engine, transaxle, and all accessaries needed for a Locost, meaning alternator only.)

Entire Honda H22A1 drivetrain, 460 lbs

Entire Honda K24A2 drivetrain, 405 lbs

Who drives shortblocks, anyway? :wink:


13lbs of that H22 weight difference are ballance shafts that can be eliminated. An aftermarket or modified intake manifold will lighten things up a bit as well since you can ditch the dual runners, egr, and fast idle thermo valve. Just something to think about.


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