clarkspeed

I’ve seen a few posts recently on the pros/cons of converting to FI and benefits of a TWM set-up. I don’t get a chance to contribute as much as I would like to this forum due to lack of time (usually working on my Z) but I wanted to write a few words on my latest adventure. Engine: What you see in the pictures is a L28, N47 head, flat tops, 1mm gasket, 490†cam, and mild/medium porting. This is NOT a street car. It sees Solo and Open track. My goal is a very quick Z running on pump gas ($). Air: Attached is an old Cannon intake with 3 x 50mm TWM throttle bodies. Attached to them are 6 K&N filters. I had to port out the intake to match the head on one side and the TB’s on the other. It was a huge amount of aluminum to remove. The intake is much lighter now. Those 50mm TB’s are huge. It works great for me but I don’t recommend for a street car. They’re like an on/off switch. I terrorize people in the pits trying to get to the track. I can cruise in 5th gear at 55, and the TB’s are barely cracked off idle so my computer wants to lean it out. In addition, there is very little vacuum to speak of so forget using a MAP for tuning. I chose the K&N’s as an economical solution to filtration. They were made for Kinsler style FI and have a tapered bell for mounting on straight tubing. I ordered and cut aluminum tubing that fit the TB’s and the filters perfect. Fuel: Injectors are from a 75 Mercedes 450 SEL, barb style, about 40lb/hour. I custom machined a Holley fuel rail blank to give the barb injectors an O-ring seal. I have a drawing if anyone wants to duplicate. It will work with stock ones also. 3/8†Aeroquip hoses deliver and all originates at an ATL fuel cell. I have a large body BMW Bosch pump and an adjustable regulator. Management: Fuel is controlled by SDS with TPS load sensing. I chose SDS for $ and built in programmer. I am very happy with it. I had to use an Innovate LM-1 to get it tuned right. Overall: Again, my car is a track car and rides on a trailer so I didn’t make many compromises. I converted from a very trick setup based on stock components. I’m happy with the TWM set-up. It looks and sounds awesome, even better than Webbers. But, I believe the gains are marginal compared to a well-ported 75’ manifold and one large TB. Again, 50mm would be way too large for a street car but works great for me. The SDS is great and I can’t say enough about programmable EFI. I haven’t dyno’d yet, but I put this engine around 225-250 hp at the crank. It had to be driven back to Orlando from the Reynolds, GA Hybrid event and got 21 mpg, BEFORE I tuned it with the LM-1. It has power and correct mixture under most all loads and speeds. Webbers are always a compromise and look at the cost of tuning them if you think that is the way you want to go. Future: The next engine will be some sort of stroker with higher compression. I built this induction system to grow into anything I might conjure up in my normally aspirated dreams. If anyone is attempting to try something similar, let me know and I can try to steer you away from any mistakes I made. Clark

I sold my 81 last year. It had 6 into 3" header. 3" in/out cat. 3" Dynomax race muffler (glass pack) before the axle. The system finished out with a 6" dia. round Dynomax straight through race muffler. It all had to empty on the drivers side. I would think a Flowmaster would fit also.

Dang! And to think I rolled mine with a hammer, dolly, and 2" pc of pipe.

Dan, If you have a jig and still interested in duplicating, Let me know.

Get the book, How to Build and Power Tune Weber & Dellorto: Dcoe, Dco/Sp & Dhla Carburettors (Speedpro) . It's better than the Haynes book and available on Amazon.

You will never get huge power out of that engine without losing the streetability, unless you go turbo. But you can make a nice street car. I just sold my "experiment in free breathing" 81 280Zx. I used a big K&N into 3" tubing before the AFM. 70mm throttle body into a heavy ported 75' intake manifold. Match ported the head to the manifold and pocket ported around the valves before a fresh valve job. Used a 6 into 3" header and ran 3" Cadalytic Converter, glass pack, and race muffler. It made a very strong street car that could dust off most other 4 and 6 cylinder cars. It came alive at 4000 rpm like a cam was in it and sounded awesome. If I did it again I would do the exhaust in 2-1/2 to get more bottom end torque and sacrifice the top end.

Ive got a set of triple 40's I'm getting ready to put on e-bay if you are interested. No manifold. I bought the set for my race car and then read everything I could about them. After pricing what it would take to tune them out I decided to go with an EFI system instead. Weber parts are not cheap!! There is a good book on them and worth the investment, "How to Build and Power Tune Weber & Dellorto: Dcoe, Dco/Sp & Dhla Carburettors" (not the HP book). From people I know that run them, 40 are great for the street, 45, 48 or 50's for all out race.

I run the Ground Control Coil Overs. If you run with their camber plates also the install fits up well. Otherwise you will end up fabricating a mount for the 3 stud towers. I don't think the brand of coil over matters much. Just the fact that you switch to the 2-1/2" springs and can adjust them is the only thing that makes a difference. BEWARE of your ride height. If you lower the car much, shortened struts are a must. Bottoming is a quick way to destroy a set of struts.

The one I bought is a 0 580 254 982 for a BMW. The one I had before was a 0 580 254 957. I don't know what it fit. Both of these pumps have the larger casing and look just like the 0 580 254 979 pump made for a 911. The only difference appears to be the inlet and outlet configurations which changes the part number. Anyway, I'm not pushing huge amounts of fuel like the big boys are but they seem to be identical. Does anyone out there have flow charts for the Bosch pumps? I could find absolutly no information or cross reference to Bosch part numbers.

Oh well, I ended up getting another big Bosch unit off e-bay for $40, new. I paid $160 for the last one and I already have a fitting for the outlet. I love e-bay! Thanks anyway, I may try the MSD or Walbro next time.

Thanks DavyZ. It's amazing what can be done with a body hammer and dolly! I have seen custom flares hammered from sheet metal and welded on that looked pretty good also. Not stock looking, but not the huge overhang you get from the big fiberglass pieces.

I wanted a very subtle flare on my Z also. Something that kept the same body lines but didn't really look like a flare. I ended up rolling out the inner fender lips and welding a piece of 3/16" round barstock to the edge for support. I gained about 1.5" of flare and almost 3" of clearance. Enough to get 245/45/16 tires under it. Looks stock unless you put it beside another Z. Here are some pics if you want to see: http://www.mindspring.com/~cstephens/zmain.htm

Keep in mind that tires are always the limiting factor in stopping distance. The stickier the tire, the faster you will stop. Brake upgrades only improve the "feel" of the brakes, durability, and fade resistance. Big $$ can be better spent on tires and wheels if you really want to stop quicker. For little money, high temp fluid, Hi-Perf pads, and ss lines go along way toward eliminating fade and providing a firm pedal.

Thanks Mike, $130 is not bad and if it works for you, it must supply some serious fuel.

Who makes a good, dependable, economical, inline fuel pump? My Bosch unit froze up after sitting for a year so I need a new one. It pulled pretty good from the fuel cell but cost around $180. Anything out there better and CHEAPER. I'm running a NA race prepared Z with SDS FI system, less than 300HP.