The Firebrid Hybrid Convertible Project (Prius platform swap)

[Bill the Engineer]

Originally Posted by cRiPpLe_rOoStEr

Though hybrids are not really my cup of tea, this project sounds impressive. How are you considering to conciliate all the gadgets in the Prius' instrument cluster with a classical look that would be expected in a good old American ride?

All will be explained. I am still a working engineer (not retired yet) so my free time is mostly on the weekends. My original plan for the dash had to change, so I will explain that in a post soon too!

Bill the Engineer

[Bill the Engineer]

Continuing with my story...

So, I had decided to investigate what it would take to convert my old rusty Firebird convertible into a hybrid. The initial research was very interesting to say the least.

At first, I thought it might be easy to just drop-in the GM Hybrid system out of the Hybrid Tahoe/Yukon SUV, since it was already a "GM" product with the same front engine / rear drive layout. Then I started looking at the specs and how poorly that system compared to my two Prii. It just seemed to be a lot of effort for not much gain. It's no wonder GM stopped making the hybrid drivetrain on that platform...

Then GM president Mary Barra made those "comments" about how GM was never going to bring back Pontiac and people should get over it. That soured me on anything GM from then forward, so the Volt drivetrain dropped off of my radar... forever.

I next took a tape measure out into my driveway and began to do some basic measurements of my Gen-III Prius to compare to my partially disassembled Firebird in the garage. Hmmm... nearly the same wheelbase (Prius a little shorter)... nearly the same tread width... exactly the same tire diameter...

OK, so if I used the drivetrain out of a Prius family vehicle, things might work out. Now to decide which Prius family vehicle to use.

My research at first took me into the direction of the hardest version to find, the Lexus HS250h. I discovered that the dash gauges were very similar in shape to the Firebird's. I even bough a salvage gauge off of E-pay to make a closer comparison.



The gauges would work, but there was the problem of the shorter wheelbase. I played around with ideas. Making the wheelbase longer by buying two HS250h was too expensive. The adjustment would need to be made by making the front fenders and hood shorter on the Firebird body. Awkward.



I also discovered that the price that a HS250h was bringing in the salvage auctions was way over my budget. The insurance companies have quite a racket going there totalling mildly damaged cars and selling the parts for a profit.

I turned to look at the Gen-III Prius which is the same platform in hatchback form. I would not have the nice instrument cluster that way, but I had hoped that the HS version would connect.



I put in a couple of unsuccessful bids at salvage auctions. No joy, but I did get to know Steve Woodruff, owner of AutoBeYours.com. He runs a Prius-only salvage repair business for mostly Gen-II Prii, although he dabbles in the Prius V wagon too. Steve happened to mention to me that maybe I should consider the Prius V since it has a slightly longer wheelbase. That turned out to be the turning point in the project. I recalculated things based on the Prius V and everything came into focus.




Next chapter soon...

Bill the Engineer

[California98Civic]

subscribed.

EDIT: and I hope the plan is to make the passenger compartment and the exterior body as cherry and original as money, time, and love can produce.

[Bill the Engineer]

Originally Posted by California98Civic

subscribed.

EDIT: and I hope the plan is to make the passenger compartment and the exterior body as cherry and original as money, time, and love can produce.

Yes. That is exactly the plan.

[user removed]

My concern is the structural integrity of a unibody vehicle with the roof removed. The original Firebird was unibody with a front subframe with 4 mounting points to the cowl-back unibody of the original car. Very marginal for strength as could easily be demonstrated by lifting the car right at the lower fender mounting points in the front of the rocker panel, and watching the door gaps double in width, when the car was new. (I know, used to adjust the gaps as a part of repair processes).

It will probably take some considerable reinforcing in the rocker panel and transmission tunnel up to and including increasing the actual height of the rockers and tranny tunnel as well as significant cross bracing of those 3 areas to improve torsional rigidity.

You mentioned two prior attempts to restore the original Firebird. I think this project will make a restoration look like a cake walk in retrospect. Estimated time, about 3k hours. Lots of fabrication since no replacement parts will be available.

A tube frame structure similar to the Mercedes 300 SL roadster, integrated into the two existing structures?

Just my 2 cents worth.

regards
mech

[Bill the Engineer]

Originally Posted by Old Mechanic

My concern is the structural integrity of a unibody vehicle with the roof removed. The original Firebird was unibody with a front subframe with 4 mounting points to the cowl-back unibody of the original car. Very marginal for strength as could easily be demonstrated by lifting the car right at the lower fender mounting points in the front of the rocker panel, and watching the door gaps double in width, when the car was new. (I know, used to adjust the gaps as a part of repair processes).

It will probably take some considerable reinforcing in the rocker panel and transmission tunnel up to and including increasing the actual height of the rockers and tranny tunnel as well as significant cross bracing of those 3 areas to improve torsional rigidity.

You mentioned two prior attempts to restore the original Firebird. I think this project will make a restoration look like a cake walk in retrospect. Estimated time, about 3k hours. Lots of fabrication since no replacement parts will be available.

A tube frame structure similar to the Mercedes 300 SL roadster, integrated into the two existing structures?

Just my 2 cents worth.

regards
mech

All good point which I will address in future postings. I thought long and hard about the issue of strength and torsional stability. Being a machine design engineer with 35+ years of experience certainly helped. The below photos will be explained later, but lets just say that I have the added strength of both car's rocker panels that will be welded together.




Bill the Engineer

[mcrews]

Originally Posted by Bill the Engineer

]

holy Crap!!!!!! VERY NICE!!!!!!

[Xist]

You are not going to drop a Prius body on the Firebird platform?

[Bill the Engineer]

Originally Posted by Xist

You are not going to drop a Prius body on the Firebird platform?

Hmmm. Never crossed my mind...


Bill the Engineer

[pgfpro]

WOW!!!

I'm also very interested in how you are going to make the floor pan more rigid?

IMO I would build a tube chassis floor bars and also add pillar foam to the rockers. I would also take some measurements from a stock Prius at the doors aperture (front to rear) and then make some temporary upper bolt in bars to set them to spec.

Very cool project!!!