re.Horsepower Chips

[lotusguy]

th4neuk said: thanks jim, cleared up a question i've been meaning to ask for a while. I assume from the post that the turbo/carb cars can benefit from a bit of tweaking??

What would you suggest is the best place to start....

Alan

Alan,

There are many areas where you can improve your n/a turbo car's performance and not for too many $$$ over a standard rebuild. I incorporated these changes into the rebuild I did to my '85 Turbo this past summer and can now easily run with the SE's. Several SE owners who have driven my car say that it even seems more capable than theirs.

Let me start by describing what I did. You can pick and choose any or all of these mods and gain some increases in performance and driveability.

First, I rebuilt my carbs, replacing all gaskets, needle valve and seat, accelerator pump diaphram and spring and rejetted my idle jets from stock 52's to 62's. The latter assisting with the 3k RPM transition.

I rebuilt the bottom end with all stock components, but replaced the old, worn, cast pistons with new, lightweight, forged aluminum pistons from JE Pistons. This increased my compression ratio from 7.5:1 to 8.5:1 . I had the pistons ceramic coated on the domes reducing their operating temp. by 150°F, thereby increasing their tensile strength by 100%, and coated the skirts with a wettable dry lubricant (molybednum disulphide) to increase oil carrying capacity. I had all engine components balanced both statically and dymanically to 0.1 gr.

Then I replaced my stock 107 intake cam with a mildly higher lift 104 cam (.412" vs. stock .378"). Along with this, I rebuilt the head having a 3-angle grind done to the valves and added bronze/silicone valve guides and thin wall higher lift springs. Again, this aids with the 3k transition. The car now comes 'On Cam' at 3k, so some bottom end was sacrificed (very little) in favor of top end performance.

My turbo was rebuilt and was over-bored to accept a roller bearing rather than the stock race bearing (this adds reliability and reduces Turbo lag). I had it balanced to 0.001 gr. @ 30k RPM.
In addition, I had my wastegate adjusted to 10 lbs. of boost over the stock 8 lbs. and finally, I had my exhaust manifiold, wastegate adapter and input (hot) side of the turbo housing ceramic coated with a thermal barrier ceramic. This had the positive effects of reducing engine bay temps by 30%, increasing the exhaust gas pressure and scavenge effect, all of which also resulted in faster turbo spool-up.

Removed the airpump and all associated hardware, plugging the air injector holes in the head w/ special BSP threaded plugs. This system is only present on US spec cars and only aids emission control on cold start-up. If you warm up your car prior to driving, as I do, this is redundant, but draws 1 to 2 horseposwer.

I swapped my 110° intake cam sprocket with the 104° ignition sprocket to advance the valve M.O.P. (Maximum Opening Point) back to it's original design spec. Again, this is a US only variant in favor of emissions.

Had the distributor recurved to apply full advance (16°) @ 2,500RPM. I advanced the static timing from 1° BTDC to 13° BTDC, giving me a total advance of 29°.

I replaced all transmission seals, bearings and synchros, added a new AP Kevlar racing clutch, new, updated clutch cover and throwout bearing. Had the flywheel/clutch dynamically balanced (this is supposed to be balanced by Lotus, but was found to be off by 4.0 gr.!)
Added a new Crossgate cable (Thanks again Calvin) and crossgate shift MOD from SJSportscars making the shift tight and smooth. Rebuilt clutch master cylinder and added new slave cylinder.

Rebuilt and powder coated all brake calipers, replaced stock rubber flex brakehose w/ stainless Aeroquip hoses, added Kevlar compound brakepads, rebuilt Brake Master Cylinder.

Finally, I added all new motor/tranny mounts, replaced all coolant hoses, replaced throttle and choke cables, added new ignition wires, 'V' belts, timing belt, rebuilt semi-automatic tensioner, replaced vacuum pump, rebuilt alternator and added the superior HC model air intake hose.

As I said, you can do all these mods/upgrades, or pick and choose. All will improve the driveability/performance of the car in some degree. Feel free to inquire about any of these mods and I can supply you with cost and availability data...Jim '85TE

>>> Edited by lotusguy on Thursday 14th November 22:56

[lotusguy]

Hi all,

Just to clarify my previous post. Except where shop services were needed for machining of parts, all of the items replaced or rebuilt were done by me with the occaisional help of another club member. I mention this as an example of what an owner with an average mechanical skill, average toolbox, set of Shop Manuals and average experience level can do. To be fair, I did have numerous club members on hand the two days when the real grunt work of removing and re-installing the engine was done...Jim '85TE

>> Edited by lotusguy on Saturday 16th November 06:36

[th4neuk]

Nice one thank you for that. Give's me some ideas as to what course of action to take.

Alan