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SCCA D Mod build questions
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Author:  Kent2 [ March 2, 2016, 8:46 pm ]
Post subject:  SCCA D Mod build questions

Hello Folks

I've been reading a bunch on building a LoCost 7 for D mod autocross, thank you for the great forum here.

Just brought home a F20c and some 1" square tubing to start with.

I have been driving an AP1 S2000 in B street and am learning while having fun.

So, what frame can I go with for D Mod rules, Book, 442, as long as it looks like a 7?

Thank you,

Kent

Author:  geek49203 [ March 2, 2016, 10:49 pm ]
Post subject:  Re: SCCA D Mod build questions

God only knows what the SCCA rules are, will be, but...

I recall at least one SCCA autocrosser that had a motorcycle engine where the passenger would normally sit?

Author:  gregk [ March 2, 2016, 11:19 pm ]
Post subject:  Re: SCCA D Mod build questions

Anything, as long as it looks like a 7, and it barely even has to do that much. Take a look at the Del Long's "Jeep" as an example.

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geek49203 wrote:
I recall at least one SCCA autocrosser that had a motorcycle engine where the passenger would normally sit?

And then the powers that be decided that bike engined locosts were just too cool for D-mod, so now they're in B-mod where they are completely uncompetitive.

Author:  Driven5 [ March 3, 2016, 4:06 am ]
Post subject:  Re: SCCA D Mod build questions

Are we talking about a fun street legal autox toy, or a dedicated (trailered) competition car?

If the former, since the book chassis is already larger than an original Lotus 7 chassis, any will technically work. Smaller is generally better, as long as it fits with your other components. Although the standard chassis is designed for a stick axle, so if using IRS you'll have to make some pretty extensive modifications to a book chassis anyways.

If the latter, taking full advantage of the rules will dictate such extensive frame modifications that you might as well start from scratch and do it right the first time anyways.

Here is the multi-time national championship winning Locost that Del built and drove prior to the Jeep...Note the engine placement.
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Author:  wrightcomputing [ March 3, 2016, 8:07 am ]
Post subject:  Re: SCCA D Mod build questions

I have built and EMod car. The main things you need to be concerned about are keeping the existing floor pan of the Lotus 7, the engine must be in the front half of the car, the driver must be completely to the left (or right) of centerline.
If you want to be competitive you need to make minimum weight, S2000 power is good, you should be able to get 250 WHP with a little work but stock power ~200whp will get it done. I would try to make the car as small as possible, mine is 106" wheel base and 70" wide. I am going to start the chassis again at some point and get it as small as possible <60" wide and <90" long. Other then that build in as much adjustment as possible to the suspension.
It does need to actually look like the original car. The jeeps don't look a lot like a jeep but they are a replica of a 1940 Jeep and the body is very close. I get complaints about my car not looking like anything.
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Do you want to be Nationally competitive or just have fun locally?

Join the DMod/EMod forum
https://groups.yahoo.com/neo/groups/SCC ... ons/topics

Author:  Kent2 [ March 3, 2016, 9:47 am ]
Post subject:  Re: SCCA D Mod build questions

Thank you for the info all, very helpful.

I'm thinking of making this a street driveable Autocross car.

Two seats dual hoop "cage". Miata donor in the future for the majority of parts.

I'm wanting to keep it tame enough the wife and kids could Autocross it also.

So any frame I go with is good, it must "look like a 7". Got it.

Author:  geek49203 [ March 3, 2016, 9:57 am ]
Post subject:  Re: SCCA D Mod build questions

Was just looking around, noting a large number of Brunton Stalkers doing D mod and E Mod. I guess the difference is engine displacement?

Just a question, why would you want to do the 442 chassis? Just to fit your motor? You DO know that a tuned GM 2.0 4-banger out of the current Camaro is a tune away from 300 hp, and a few more tunes away from a ton more than that, right?

Author:  1055 [ March 3, 2016, 10:00 am ]
Post subject:  Re: SCCA D Mod build questions

There's a couple replacement for displacements.. notably, forced induction and rotaries.

Though last I saw, our local organization (CART) did all sorts of whacky stuff when it came to classifying rotaries..

EDIT: Nevermind.. they follow SCCA classing rules now.

Author:  Kent2 [ March 3, 2016, 11:01 am ]
Post subject:  Re: SCCA D Mod build questions

geek49203 wrote:
Was just looking around, noting a large number of Brunton Stalkers doing D mod and E Mod. I guess the difference is engine displacement?

Just a question, why would you want to do the 442 chassis? Just to fit your motor? You DO know that a tuned GM 2.0 4-banger out of the current Camaro is a tune away from 300 hp, and a few more tunes away from a ton more than that, right?



I'm a Honda guy, so sticking with a Honda powerplant is for me. I did think about a K20, but in the end the F20 was cheaper.

I do want to make the cockpit big enough so regular size people can fit, or even regular American people.

Author:  wrightcomputing [ March 3, 2016, 11:19 am ]
Post subject:  Re: SCCA D Mod build questions

DMod is <2.0L
Forced induction = x 1.4
Therefore the largest turbo engine in DMod is 1.4L (1.4L x 1.4 = 1.96L)
Emod <3.6L = 1700lbs
Emod >3.6 = 1800lbs

Penalty for modified tub (automatic on rube frame) +50lbs
<51% weight on rear tires = -50lbs

Not sure of DMod weights but I think it is around 1200lbs

Author:  geek49203 [ March 3, 2016, 11:31 am ]
Post subject:  Re: SCCA D Mod build questions

Kent2 wrote:
I do want to make the cockpit big enough so regular size people can fit, or even regular American people.


My Haynes is 221, and my American-sized (donkey reference)(6 foot, 220 or so pounds) fits w/o any issues. The driver's butt width (EDIT -- uh, the space in the car, not the width of the human, ed) is almost 20" wide in mine, and 18" for the passenger. For comparison, my kitchen chair is only 17" wide.

IMPORTANT SAFETY TIP -- do NOT measure the width of your wife and/or girlfriend's (donkey reference) when building your car, at any time!!

But then again, my almost same sized frame fit (snugly) into a genuine Lotus Seven S2, which is around minus-3 to "the book" (or 7" shorter, 7" narrower, etc than your proposed frame). It was like getting into a sleeping bag w/o unzipping it, and I don't think I could drive it w/ my shoes on, but.. I fit and I could drive it. I'm betting that a good number of "American sized" people who don't shop entirely at Robert Hall / Lane Bryant would fit into the the original.

How did the Seven do it? Well, first off, the trans tunnel in our builds are, by comparison, massive -- 8" wide at the hip. The original Seven didn't have a frame running down that tube -- it was just a bit of aluminum sheet -- and if I recall correctly, the drive shaft is maybe 2" in diameter, so the entire hump is only 5" wide. EDIT -- the S2 had 16" butt spaces for both passenger and driver. /EDIT The original also had no side padding for your hips -- your butt sits on a "Bench" and you've got the aluminum drive tunnel on one side, and the aluminum/tube side panel on the other.

Author:  Kent2 [ March 3, 2016, 11:33 am ]
Post subject:  Re: SCCA D Mod build questions

To answer what I am going for on the level of the car, maybe both...... :D

I'll be heading to Lincoln a few times this year, the Midiv and Nationals. Maybe another if I can squeeze it in. All in my S2k.

I'm looking to have a running car in 2+ years, so no rushing on my part.

Book chassis is what I'll start with, thanks for the info on keeping it small.

Author:  Kent2 [ March 3, 2016, 11:48 am ]
Post subject:  Re: SCCA D Mod build questions

I'm seeing min weight with driver 1420

That is the 1801-2000cc and +40 on Mod tub.

Light, that is very light.

Author:  geek49203 [ March 3, 2016, 11:55 am ]
Post subject:  Re: SCCA D Mod build questions

Kent2 wrote:
Book chassis is what I'll start with, thanks for the info on keeping it small.


The bug fix / update for "the book" is the Haynes book. It has a ton of the common mods done to the Book, as well as fixes a couple of mis-measurments, etc. PERSONALLY I'd use those plans, looking for someone who's got a Honda donor build going along the way. The Haynes is a 221 chassis.

http://www.amazon.com/Build-Your-Own-Sp ... 1844253910

https://haynes.co.uk/forums/index.php

There are plans around (and a few builds done, including at least one here) using the Miata as a donor.

Author:  horizenjob [ March 3, 2016, 12:13 pm ]
Post subject:  Re: SCCA D Mod build questions

Quote:
I'm wanting to keep it tame enough the wife and kids could Autocross it also.
So any frame I go with is good, it must "look like a 7". Got it.


I had about the same goal for my car. Design it for track use and then build t for track or street use. You don't have to use stiff springs or a peaky motor but it can't hurt your street car to have a well designed frame or suspension.

For me that meant a car with a cage of some type so that lead to designing Car9, which has a locost style frame integrated with a roll cage. It's just stronger and simpler that way, it also gives you more room inside because it doesn't need the traditional locost frame transmission/driveshaft tunnel. I also wanted IRS ( which is a big improvement in ride for a street car ) and stronger structure around the fuel tank and real support for the roll bar.

My frame has a low front hoop, like the Jeep above. If you want a tall front hoop, that would be doable too it would seem.

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