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Learning how to build Lotus Seven replicas...together!
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PostPosted: January 8, 2017, 11:41 pm 
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Joined: April 15, 2011, 10:39 pm
Posts: 94
Location: Dallas, PA
I'm looking for input on engine choices for my next build. My first build had a Toyota 4AGE with dual Mikuni carbs and was fun for 120hp. I've since had the pleasure to drive several more 7-esque vehicles with everything from a 1275cc BMC to a modified Kent, a Yamaha R1 and my turbo 13-B rotary. I'm going to get finished on the Honda F20C car for my father and then concentrate on building something else for myself. It will be a trackday and hillclimb car, no street duty. I would like to see in the ~250hp if NA or 300hp if turbocharged. I have narrowed it down to the Toyota 3SGE BEAMS or Honda F20/22C if staying NA as they should be capable of nearly 250hp. The SR20DET can easily make 300hp but I'm not that familiar with that motor and not sure if I want to deal with turbo lag in a very light weight car.

Any insight would be greatly appreciated.

Thanks for your time and have a Happy and Safe New Year,

Dan

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PostPosted: January 10, 2017, 4:43 am 
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Joined: January 5, 2017, 11:36 am
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I only have experience with the fwd sr20 and sr20det from your list. But have looked into the beams quite a bit. Sr20s or any motor won't have lag if the turbo you are using is sized right. You really want the turbo in full boost half way through your rpm range or so I think the rule of thumb goes.

On my nissan nx2000 I have a factory t25 (they seem to max out around 280whp), it is too small for the motor really. the factory gtir t28s are larger but not much (maxing out around 300whp) . The t25 stops making power before it redlines the rpm. The power comes on instantly (maybe around 1500-2000rpm at factory boost levels (7psi spiking at 8-9). Thats enough to spin 1st and or 2nd gear up to redline from just stomping the go pedal. At higher boost levels it will roast the tires through more gears ( keep in mind the gearing is for a N/A car so it's partly that too). With some fuel system/ecu upgrades and a boost controller you will wish you had some lag... (I think the 3sge has a smaller turbo too but it seems like less of them around so not 100% on that).

In rwd form there is lots of aftermarket and used parts around for the sr20 and the f20. I would pick one of those two finances depending.


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PostPosted: January 11, 2017, 12:39 am 
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Joined: January 10, 2008, 4:47 pm
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Location: Massachusetts
If your last build used an F20, then maybe stay with something you know?

I wonder what your hillclimbs will be like. I managed a 1st place at the Reading Hillclimb back when people still used actual stopwatches... :rofl: I also had a couple of FTD's in Vermont. In that later case I would be very cautious with a turbo or getting over powered. Driving my car on the straights was like walking on eggshells. It was around 100 MPH on a road with a 15 MPH speed limit and extensive frost heaving. The car was airborne so much of the time because of the rough pavement that it was weaving a bit.

My formula ford only has 106 HP and about 1100 lbs. With a lot of power and especially turbo lag there could be an unhappy result.

Here's a video of someone that had a 200+ HP Caterham I think. It's an old video but really well made, I think he had a job in film production. There are some other videos he made too.
https://www.youtube.com/watch?v=ntsNfMTyQnQ

Here's some Porsche abuse...
https://www.youtube.com/watch?v=_dPFkpBbq_E

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PostPosted: January 11, 2017, 9:56 am 
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Joined: October 19, 2012, 9:25 pm
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I just built an SR20 Locost. I can tell you that it's a handful when it comes under boost.
Rear tires were 200 treadwear Avons that are SUPER STICKY. I'd light up the rear tires every time I rolled on the throttle trying to autocross it.
I added 300 lbs or ballast to the rear frame and it settled some, but was still easy to swap ends.

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PostPosted: January 11, 2017, 12:02 pm 
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Joined: September 22, 2005, 10:29 am
Posts: 342
What about Honda K series? They've been out so long that the prices are a lot more reasonable than they were. It seems to me that for all the trouble that goes into a build, why wouldn't you spend another thousand bucks and get an easy 225-250 HP?


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PostPosted: January 11, 2017, 8:16 pm 
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Joined: February 8, 2007, 4:20 am
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Location: British Columbia, Canada
If you do decide to use a K series Honda, there are adapter kits available to attach it to a Miata transmission:

https://kmiata.com/

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PostPosted: January 11, 2017, 8:23 pm 
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Joined: September 22, 2005, 10:29 am
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mainlandboy wrote:
If you do decide to use a K series Honda, there are adapter kits available to attach it to a Miata transmission:

https://kmiata.com/


And yes, they will sell individual pieces of their kits. I asked. No need to buy things like the subframe if you're building the entire chassis.


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PostPosted: January 11, 2017, 8:36 pm 
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Joined: April 1, 2010, 10:26 am
Posts: 298
I am running a KMiata setup with a K24A2 engine, I love the engine, it dynoed at 218 rwbhp bone stock. It turns out the S2000 inlet setup is not the best way to go on our engine bay configuration. So I could have saved some money going for the rear intake inlet manifold and saving the cost of the S2000 manifold adapter. The Civic SI RBC manifold would be perfect. But the engine is perfect very flat torque curve.

Graham


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