A Turbo 13B EMod Locost

[seven13bt]

Well, the RX7 is too much of a size and weight compromise for the local autoX events, so I've started on a Series-3 size Locost that will be narrower than a Miata and meet the lower weight of about 1,500 pounds for the car. The power will of course be from a dry-sumped 13B turbo.
The chassis has been finish welded and the torsional stiffness was measured at 3,300 ft-lb/degree. The "boot" has been made to be easily removable for access to rear suspension and differential. The passenger diagonal bar and the leading transverse bar above the transmission are removable to allow the trans to come out through the passenger area.





Caterham build over several decades (sold): viewtopic.php?f=33&t=13185#p133846
Locost build with 2.0 Duratec and 1.4 turbo Ecotec (sold): viewtopic.php?f=35&t=19213#p236350
Tubeframe RX7 build: viewtopic.php?f=36&t=20382#p251528

[RTz]

YES! Welcome back to the dark side

[Miatav8,MstrASE,A&P,F]

Looks great! It flows. You could probably shave a foot or so off the front bringing the rear lcap even with the crank pulley but I guess you are keeping it to scale.

You could greatly reduce the scrub and lose some sprung and unsprung weight by making a bolt on lbj plate that fits on the bottom of the upright, lbj ball housing attached to the upright (higher ball brings the zero scrub line outboard and allows a lighter frame with higher lower rails up front) and the lca lbj boss is smaller for more clearance to the rotor in full bump.

[seven13bt]

RTz, Thanks for the welcoming. It's the "added lightness" that brought me back.
MV8, It's prolly just the photo perspective that makes the scrub look bad. The fabricated upright and the Wilwood M2 upright on my RX7 use the same wheel with a 6 inch backspace and both have a 3 inch scrub radius. It works fine on the RX7, which is a heavier car.

[seven13bt]

Been working on the oiling system, the cooling system, the intake and the exhaust. They're each about 90% done. Everything will be coming out so that the items that have been welded in recently (as well as some that are yet to be added) can be painted. Then the transmission will be getting new synchros. After that and reassembly, the fuel and electrical systems will be added, with the goal of making noise. The clamshell fenders will cover radiator and most of the exhaust.

[KB58]

Oh! Excellent! You're the first locost builder I've seen to figure out that placing the turbo outside the engine compartment makes a lot of sense. Someone finally listened to me... even if it wasn't you!

[seven13bt]

Hi Kurt,
Thank you for dropping by and thanks for the thumbs-up.

Ron

[JackMcCornack]

The chassis has been finish welded and the torsional stiffness was measured at 3,300 ft-lb/degree.

I'm working from memory here, but I'm pretty sure that's more than double the torsional stiffness of a book Locost. Tell us your secrets!

[seven13bt]

Hi Jack. It's some extra triangulation and the forward down-bars for the roll bar.
The frame tested at 2,100 ft-lb/degree without the roll bar, down-bars and the triangulation that joins the right down-bar with top plane in the middle of the car (the yellow arrow).

[RTz]

Looking great. Would you be interested in sharing your method of measuring torsional stiffness?

[seven13bt]

Hi Ron,

It's on the second page of this build:
viewtopic.php?f=35&t=19213&start=15
The entry is on Sat, Jan 20, 2018, but ask any questions that this may not address.

Ron

[kreb]

Very nice. That's one honking large intercooler! May I ask why you chose a rotary?

[seven13bt]

Kreb,
Yes, you may ask. I chose the rotary engine because they are a small package, have a low CG, can produce the 400 HP needed reliably and I have 32 years of experience using them in race cars.
The intercooler isn't any larger than the one used in my RX7, it's just that this one has larger end tanks due to the direction of flow. This one is more efficient because it has a greater average delta-T.

Ron

[kreb]

Thanks. I've always liked rotary's for their free-reving personality, and never had a lick of trouble with the 13B on my RX7. Cool choice.

[Tadbaker]

Been working on the oiling system, the cooling system, the intake and the exhaust. They're each about 90% done. Everything will be coming out so that the items that have been welded in recently (as well as some that are yet to be added) can be painted. Then the transmission will be getting new synchros. After that and reassembly, the fuel and electrical systems will be added, with the goal of making noise. The clamshell fenders will cover radiator and most of the exhaust.

Let me know when you are going to have it make some noise. I'll try to be there.