Porsche 914 Conversion - Dedicated AX Racecar

[Jaxx]

pictures links are dead

fixed

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[AND0]

Pictures work okay for me.

Is the Lotus steering rack any faster then the 914 setup? From the videos it really looks like you could use a faster rack.

[Britain]

Originally Posted by Matt Monson

As always, thanks for being so open with your porject. One thing that I will throw out there for you to consider as you weigh your options is that if you build a 915 gearbox on a '72 or '73 case you can move over your current TBD without reinvesting in a new unit as long as you continue to use a 7:31 cwp ratio. A lot of guys don't realize that the early 915's used the same carrier dimensions as the 914 and can be swapped back and forth.

If I go the 915 route, it will be a Mag case and have some special parts inside to increase strength.

Yea, I know I can use the TBD on a 7:31, but can it be used on a 8:31 with spacers or anything. I still need to work out the ratios I need, but the 8:31 would be nice in terms of strength.

Do you happen to have any of the straight-cut 915 left?

-Britain

[Britain]

Originally Posted by AND0

Pictures work okay for me.

Is the Lotus steering rack any faster then the 914 setup? From the videos it really looks like you could use a faster rack.

Do the pictures work for everything now...not sure what was going on there.

As for the rack, yes...I need a faster rack. I am not sure if the Lotus is faster than the stock 914 rack...pretty sure it is.

-Britain

[Matt Monson]

Originally Posted by Britain

If I go the 915 route, it will be a Mag case and have some special parts inside to increase strength.

Yea, I know I can use the TBD on a 7:31, but can it be used on a 8:31 with spacers or anything. I still need to work out the ratios I need, but the 8:31 would be nice in terms of strength.

Do you happen to have any of the straight-cut 915 left?

-Britain

Britain,

In short we can make anything. We're about to start a limited production run of straight cut synchro gears for a genuine SC-RS over in Europe. Something like that doesn't cost any more, it just requires lead time over the ratios I usually keep on my shelf.

Or do you mean straight cut dog box stuff? To be honest, you don't want that stuff. I've got some of it leftover but that kit never got fully developed and required a lot of BS fenagling to make it work right. I'm not a big fan of it. If you go that route with it, You'll want to have Hayden personally build the gearbox. He's on top of the issues and the tricks required to make it work properly.

The challenge then becomes gearing. Correct my thinking if it's wrong, but you'd want to do something similar to your current box with just 2 usable gears. Obviously you don't want to cross gates on your shifts and with the change in shift pattern from the 914 to the 915 you've got to pick whether you're going to build it on the 1-2 axis or the 3-4 axis. Personally I would probably do it on the 3-4 axis, in which case, there's not a 3rd gear we've made in the past that's appropriate for your needs because none of them will be short enough for your launch.

If you go with the 1-2 axis, that's more straight forward but then it adds a lot of extra expense because you've got to replace the mainshaft since 1st is fixed to it. That does open you up to using a 300m mainshaft if you want, which has its advantages, but it's a question of dollars and cents.

If it was my car and I was going with a 915 I'd probably leave the stock mainshaft in there, along with 2nd gear, and then build my race ratios around 3rd and 4th. I would do them with 930 synchros and dog teeth instead of standard 915 ones (same as the 901 synchros in your current box). Straight cut but still synchronized

We are going to redesign the 915 dogbox at some point in the next couple of years, but it's in line behind our GT3 sequential gearbox and our Cayman seqeuntial gearbox projects. It's a ways off yet.

You can make an 8:31 ring and pinion fit an early case with a bit of fiddling. The ring gear flange is 2mm thicker, but that can be compensated for with alternative carrier bearing shims. The other option, that you may not be aware of is that we make an 8:35 cwp set. It's what Porsche used on the SC-RS once the cars had exceeded the strength capabilities of the 7:31 but still wanted something short.

Feel free to ping me if you wish to talk about any of this in more detail privately.

Regards,

Matt

[7m-gtte]

How the build coming?

[Britain]

Some great updates as we get closer and closer to having the car on the track.

First up, exhaust. Since we ran out of room to route the exhaust out the back of the car, I had to modify the arrangement to allow it to be routed out the side of the engine bay. Here is the new wastegate plumbing completed. I added a second flex joint to make installation on the second wastegate a bit easier. Also got the nice V-Band for the muffler connection.



Another view of the wastegate plumbing. Getting the joints to line up took quite a bit of time.



With the muffler attached.



Here is the complete Sub-frame back out of the car ready for final welding, painting, and then reassembly.





Engine and transmission reinstalled in the sub-frame.

[Britain]

On to the interior...or cockpit I guess since there is not much interior.

Cockpit is all ready to go. Switches mounted, remote brake bias adjuster installed, dash mounted...



Fuel tank enclosure completed and tank/fuel pump mounted.



View of the fuel tank enclosure from the front.



Fuel tank enclosure door closed and tank seals from inside the car completely.

[Britain]

Now the exciting bits.

Got the custom set of Olhin shocks.



Front shocks installed on the inboard rockers.



Close-up view of the front shocks installed.



View from below of the rear shock and suspension.



Clearance the rear trunk lid for the new cage bars. The holes are not as bad as I thought they would be.



Master Welder Evan working his magic on the last few cage bars. As of now, all the major welding is completed.



Due to the new position of the cage I had to find and modify another engine lid to clear the bars.



View of the modified engine lid in the up position.



I previously mounted the vehicle speed sensor to the outside of the inboard CV, however this interfered with the springs. Therefore I had to weld it to the inside of the transmission output shaft and reverse the sensor mounting. Also added a mount for the hydraulic clutch lines.

[Britain]

New GT Racing rear flares installed. Might need some slight modification, but at least they clear the wide wheels.



Back view of the car with the rear flares installed.



Top view of the rear fender width.



Good lower view.



This is one of my favorite views....talk about wide!

[Loubaru]

This car is insane... one of my favorite builds on the internets. I'm assuming you own XP with this monster?

[UWMechEngr]

Originally Posted by Loubaru

This car is insane... one of my favorite builds on the internets. I'm assuming you own XP with this monster?

Fred Zust's "FrankenLotus" is the national XP killer right now. It's also a hell of a build thread. I hope Britain will give him a run for his money this year though.

Britain, we've never met, but I've followed this thread, it's looking amazing, and I hope I get to see it at the Packwood NT this year.

[sti4rs]

Coming along nicely. Can't wait to see it race!

[Britain]

Thanks guys.

I sure hope that it is a national contender in XP, I just want to be in the top 3 and have a chance at an upset. Fred's XP Lotus is one hell of a car.

The plan is to try to make the San Diego NT, definitely make the Packwood NT, possible make the Colorado NT, and definitely make the Nationals in NE...we shall see.

-Britain

[Matt Monson]

Britain,
I hope you make the Colorado event. I would love to see this work of art up close and personal and meet you. That new subframe is just out of this world. I hope someday my '73 will look something like that. Just plain wow.

[Britain]

She is alive!

I didn't get to drive it yet, but the car successfully made it through a set of shake down runs at El Toro this past weekend. Still needs proper bodywork, ride height lowered, sway bar, new tires, proper brake pads, cage painted, replacement ball joint, and some spring changes...but it is getting closer.



-Britain

[7m-gtte]

Good to hear. Looking forward to a video.

[ryansport22]

I first saw your car at a autocross in Eugene a year or two ago, looks like you have been busy sense then. Well now my car is in XP too and I'm going to do my first national tour event at Packwood this year. It will be fun to race with you, Ill come say hi at some point.

Ill be in this

[K.Linchpin]

ryansport22, nice dude! GL if u know what I mean.
Also, hook that thing up with a p1 wide body kit so it looks the part!

[ryansport22]

I know what you mean by "good luck", Ill just be there to have fun and learn about racing at national events. Now if its raining things might be a little more interesting!

[Britain]

It has been a few weeks since I last posted, but in that time we have ran the car at the San Diego National Tour and the El Toro Pro Solo. Both weekend were not without issues, but we are getting much closer to completion.

I will start out with the San Diego National Tour weekend. I arrive a day early to get everything sorted out on the car and ensure that it was ready. We spent quite a bit of time on the small stuff, including several hours to get the car corner weighed and aligned. There are just so many adjustments that it takes a while to get them all working together.

Once we had everything completed, it was time to test drive it up and down the street in front of the shop and get it loaded up. Just as we were about to load it in the trailer, the transmission decided to grenade and no longer function. We pushed it into the shop and were able to pull out the transmission, rebuild it, and reinstalled in 1hr and 9mins....it ended up just snapping the arms off the slider hub and we upgraded to a later model 915 slider which is much thicker.





With that fixed, we headed to San Diego.

Since the shake down runs, we added a front blade adjustable sway bar, lower the spring rates, upgraded to racing brake pads, and put on the new tires. It was basically a new car at this point. We basically spent the entire event making set-up adjustments and reteaching our brain how to drive this think. It is odd to get into a car that you have been driving for so long and to break all those habits that it took to make the previous set-up work.

Here are some pictures of the car in San Diego. The ride height is about 2.5inchs higher than optimal because the front wheels would hit the fender thru the turning arch. The set-up that I went with is QRS Fiberglass front fenders widened about 1.5" and GT-Racing Rear Fenders.







The next weekend I returned to So-Cal to run the El Toro Pro Solo. This time around we had time to cut the front fenders for more tire clearance and lower the car to the desired height.



Unforeseen issues with this new ride height was that the front lower control arm was hitting the sway bar bracket under bump and therefore resulted in the car having basically "infinite" front spring rate. This explained the bad corner entry push and corner exit snap-oversteer that occurred the first day of the event. We returned to the shop to relocate the front sway bar to a higher location to gain the necessary clearance.

The car showed much improvement while running the next day. However, now under hard breaking on corner entry we had the splitter hitting the ground and the wheels rubbing the inside upper fender well due to the car sitting too low. This really cause the car to get upset on low-speed corner entry and greatly effected my run times.

I have since raised the front end, reset the bump steer, set the toe and I am ready to go racing again this weekend for further development time.

I will get some more pictures posted soon, I have spent most of my time underneath the car with dirty hands.

-Britain

[DrieStone]

Not trying to hijack this thread, but it seems somewhat related. I own an '83 Lotus Esprit, and I'm currently in the process of an engine rebuild for it. However the original engine is carbs (and nearly impossible to get parts for). If I were going to do an engine swap, the WRX engine seems like a reasonable replacement.

One of my fears though is that the transmission would be too long (specifically the distance between the "front" axle shafts and the rear of the transmission. Does anyone have an idea what the distance is?

[Britain]

Small updates to the car as we continue to get it sorted out.

First up, transmission refresh. When we were in there replacing the busted slider hub a while back, I had noticed a small crack forming in the cage of the large roller bearing in the intermediate plate. We didn't have a spare on hand at the time so I had to go back and replace this part. I am glad I did as the crack had grown and who knows how much longer it would have stayed together.



Next on the list of "upgrades" was to get rid of the 40+ year old Porsche steering column. Combination of flex in the column mounts as well as a worn out inner bearing was causing noticeable movement of the steering wheel under load. My plan was to install a steering quickener to serve as the new steering column.

Here is the Porsche steering column:


My first attempt at this employed a 2-bolt steering quickener with an extension shaft machined and a plate with the Mom hub pattern waterjet cut. Here is a comparison of the Porsche steering column next to the Steering Quickener piece.



Here is the set-up installed.



While it did greatly increase the steering response, basically 1 turn either way to hit lock, it didn't improve the lateral movement of the steering wheel. After a bit of research, I found that Coleman actually makes a 3-bolt version that is actually intended to be a steering column type piece.

Here it is installed with additional bracing.


Much better feel and a whole lot less lateral movement. We also extended the wheel out closer to the driver by about 1" to improve the drivers leverage on the wheel.

Here is the cockpit back together.



-Britain

[Britain]

The other major update was a new clutch/flywheel package. I was previously running a Tilton single disc set-up and was right up against the load rating for the set-up and therefore wearing out clamping plates and friction discs very quickly. In addition, the Tilton parts were getting harded and harded to find as they stopped making a lot of components.

The new set-up consists of another custom machined flywheel and a Sachs dual plate set-up. This unit is rated at 600ft-lbs and should be plenty strong enough to handle my measly power

Here is the old set-up next to the new one:


Here is the new flywheel and clutch package, the flywheel is a piece of art...and cost about the same.



The flywheel is unique in that it has a center plate that is installed over the flywheel bolts to capture the nose of the transmission mainshaft.



Installed and all torqued down:


Everything back together, clutch bled, ready to do burnouts.


We ran the car this past weekend and the new clutch has a great feel and works great!

-Britain

[RSti_Spyder]

Very nice as always. Who built that beautiful flywheel?