By David Swingle, owner
DeLorean Motor Company Midwest
Crystal Lake, IL
This is a follow-up to my story about DeLorean restoration that was published by Underhood Service in October 2010.To view that article, click here.
This article explores performance modifications that have been developed for the DeLorean from the time of its release to the present day.
Although anything is possible, performance modifications over the past 30 years have focused primarily on the areas of engine modification (or replacement), and suspension modifications. I won’t be getting into time travel modifications those are beyond the scope of this article.
One of the earliest criticisms of the DeLorean was its lack of power compared to its contemporary sports cars.
By the standards of the day it was considered heavy (2,800 pounds although that seems light now!) and the original engine was rated at 130 hp net, significantly choked by the exhaust system design and single catalytic converter used for packaging reasons.
A typical stock, well-maintained DeLorean tested on a chassis dynamometer will rate in the 95-100 hp range at the rear wheels.
The engine itself is a single-overhead-cam 90° odd-fire 2.8L V6 known as the PRV (Peugeot/ Renault/Volvo) B28F. Fuel injection is mechanical Bosch K-Jet+Lambda.
This engine was relatively common in Europe at the time, although it only made its way into some Volvos and later Eagle vehicles in the U.S. market.
The block is aluminum alloy with separate (wet) cast-iron cylinders and aluminum two-valve heads. The cams are driven by separate chains. The engine timing cover is a single V-shaped plated that looks similar to some modern Ford engines.
This design does cause one issue with common performance tweaks excessive milling of the heads will cause cam timing to be slightly retarded and can cause oil leaks at the valve covers if not addressed. As the engine was originally architected as a V8, the crankshaft and bearings are very robust, as are the connecting rods. The internal weak spot is the cast pistons.
There are two transmissions used in the DeLorean, a five-speed manual and a three-speed automatic. The manual is the Renault UN1. It’s capable of supporting close to two times the power of the stock DeLorean engine, although the stock clutch as installed in the DeLorean is probably the weak point. The only transmission modification typically performed is to install a more bulletproof input shaft coupler. For some reason, the OEM coupler is missing several splines.
An aftermarket coupler is available that is made of more robust material and is fully splined.
The automatic is also a Renault unit; it’s a very basic three-speed transaxle with electronic shift control (no overdrive, no locking converter.) While adequate for the car, it’s not a high-capacity unit and is probably not tolerant of much above 200 hp.
There aren’t many other transmission options for the DeLorean. Due to the relatively unique rear engine layout, the only thing that can be made to fit is something from Porsche. Unfortunately, used Porsche transmissions tend to be extremely expensive, so you won’t see them used much.
They also present some interesting installation issues, as they are wider that the DMC transmissions and the output shafts tend to be located differently. Amazingly though, Porsche output flanges will bolt right up to DMC half-shafts.
The DeLorean Motor Company was well aware of the power deficiency relative to other sports cars of the day, and had contracted with OEM tuner Legend Industries to come up with a factory turbocharger option. Legend was known at the time for developing kits for other European makes, notably Fiat.
They did build and test several prototypes for DeLorean that utilized twin intercooled turbochargers and extensive internal engine modifications. Unfortunately, the failure of the DeLorean Motor Company killed off the program as well as the Legend company.
(See Photo 1.)
This project held quite a bit of promise for the power living up to the looks of the car. The original prototype vehicle is still in existence in a private collection.
An aftermarket twin turbocharger kit was released shortly after the demise of the company. Developed by a small Long Island, NY, company called Island Turbo, this $5,000 (in 1982!) kit was typically installed by shops or adventurous owners.
It consisted of two tiny IHI turbochargers, custom-cast exhaust manifolds, custom-cast intake plumbing, extra oil plumbing, two small resonators used as mufflers and some minor tweaks to the engine’s Bosch L-Jet fuel system to provide full-throttle enrichment. Ignition advance was limited via a modification to the OEM distributor.
(See Photo 2.)
This system eliminated the factory catalytic converter. Island later came out with a revised system that replaced the mufflers with small catalytic converters, but not many of those modifications were sold.
A second aftermarket kit was sold by a West Coast company, BAE. This was a single, larger Rajay turbo that bolted on in place of the catalytic converter and used a different muffler setup, but maintained the original exhaust manifolds and crossover. Other modifications to the engine were similar to the Island twin setup.
Both of the turbo kits were limited to about 5 psi of boost, as no internal engine modifications were made during the installations. Both kits yielded approximately a 40% power increase, quite noticeable to the driver, but not enough to hurt other parts of the drive train. The real problem with the turbo system was that heavy use of the turbo boost would overpower the engine’s PCV system and make the engine tend to leak oil from the crank seals.
You can often note a turbocharged engine car on first glance because the engine looks excessively dirty. Another common problem, and much more serious, is that some owners would try and adjust the wastegate for more boost without making other modifications. This would lead to a lean condition at high rpm and the resulting detonation would lead to broken pistons.
I know of no sales figures for the two systems, but based on seeing such cars in the wild, it was likely not more than a hundred. Parts for both turbochargers are getting hard to come by 25 years later, so it’s relatively common to convert the cars back to naturally aspirated operation when the turbochargers fail (usually failed seals leading to high oil consumption).
This conversion requires removing all the turbo parts, re-acquiring the missing portions of the stock exhaust, and un-doing a few other modifications to the cooling system and ignition distributor, as well as filling in oil drain holes that had been drilled into the engine crankcase for the turbo. It’s also a good idea to tear down the engine and check for broken pistons, especially if more than the usual blow-by had been noted or if the engine fails a compression test.
It has never been particularly common to perform engine swaps on DeLoreans, but as with most cars it’s certainly an option and there are always people willing to try. The biggest drawback to such modifications is that they tend to be under-engineered and un-documented, so anyone after the original shop/owner has a hard time maintaining these vehicles. They tend to have dramatically diminished salability. This needs to be strongly considered when thinking about doing an engine swap on one’s own car.
Early on, a popular swap was one of the Buick 3.4 Grand National turbo engine variants. Being a 90° V6, the fit into the car was similar to stock although engine mounts had to be fabricated. It was apparently common enough that someone came up with a factory-made custom bell housing to mate the engine to the DeLoean manual transmission.
This engine can be modified to 300 hp or more, so transmission damage is something to watch out for. It is also quite heavy compared to the stock PRV. There was one notable Gale Banks Twin Turbo Buick installation done in the mid-1980s. At present, like the turbo options, parts supplies are pretty scarce and/or expensive even relative to standard DeLorean parts.
Other swaps that have been done over the years include a Ford 351/Pantera drivetrain (it required extensive frame modifications as well), small-block Chevy, 4.3 Vortec Chevy, Mazda three-rotor, Cadillac Northstar and, more recently, a Nissan VQ35/Porsche transaxle setup.
This last one presented some interesting engineering challenges, due to the combination of a Japanese engine to a German transmission in an Irish car! This particular conversion is considered very successful and is still on the road today in the hands of the person who did the conversion.
One engine swap that isn’t quite in the same league as the above examples is the installation of an Eagle PRV engine. This is an engine that was used in the Eagle Premier/Dodge Diplomat into the 1990s, so it is not exactly a common engine either. The primary advantage to this engine is that it’s a direct bolt-up to the DMC transmission (engine mount modifications are needed).
A secondary advantage is that they are cheap engines to obtain. The benefits are slight; it is an even-fire engine and has slightly increased displacement over the stock PRV. The Eagle engines are all electronically fuel injected so they are logical bases for conversion to an aftermarket EFI system (more on that later).
Basic Engine Modifications:
Although the PRV is a pretty uncommon engine in the U.S., there has been some work done to modify it based on common hot-rodding techniques and on modifications developed in Europe, where the engine is much more common. There have been several cam grinds developed, high compression pistons from a couple of vendors, low compression forged pistons to beef up turbo installations, etc.
There have also been several header options. Headers can be a packaging challenge due to the rear engine design and limited space for mufflers and converters, while keeping runner lengths equal. There are several exhaust options on the market, but most of them do not make provisions for catalytic converters.
There are several owners at this time who have converted the car from the K-Jet to a modern EFI fuel system, typically using a MegaSquirt EFI computer available in the aftermarket. This is a very labor-intensive effort to install and get tuned to where it is as reliable as the original, and isn’t any cheaper. There is still development work needed before this can be considered a common modification.
Another modification that has gained favor recently is converting the engine from the original Bosch K-Jet mechanical fuel injection to a carburetor setup. This is not really seen as a performance modification and is done more often to save money over the cost of properly restoring the Bosch system. This is also a modification that can impact resale value as it is typically a homemade setup without documentation and minimal engineering.
Stage Engine Kits:
DeLorean Motor Company of Houston, TX, undertook a project in the early 2000s to have performance packages engineered as a complete system, with a goal of maintaining the original K-Jet system and providing a path for owners to install upgrades sequentially without losing prior investments. This has become a very popular setup, and are the most common engine modifications being done to the cars at this time.
This is the only setup that has been engineered as a complete system rather than grouping of modifications (cams, ignition, etc.) from various sources without detailed study and measurement of the interactions. It’s also the only design that is 50-state emissions legal using two catalytic converters and maintaining the O2 sensor.
See Photo 3.
Stage 1 is an engineered exhaust system, which comes with a cold-air intake setup and performance air filter. This is an equal-length header system. The original version was coated steel, but that has been changed to the current product, which is fully stainless. Stage 1 can be bought “over the counter” for self install, or installed at one of the DMC family of shops.
Stage 2 is a further engineered set of engine modifications that consists of the above Stage 1 system with the addition of modified camshafts, flow work on the heads, and replacement of fuel injectors and ignition system at the time of installation. As this system requires exchange of cylinder heads, it is very popular with owners when a vehicle needs head or exhaust gaskets anyway.
This option has been dyno-tested at a 40% power increase. This is similar to the gain from the turbocharger setups, but as it is strictly a “breathing” modification, the ill effects of the turbo setups do not occur.
Stage 2 is only available for DMC shop installation due to the complexity of the work and the room for error installing heads. It is possible to buy a Stage 2 on a complete engine, where the modifications are installed on a “fresh” engine and shipped complete.
Stage 3 (currently in development) is the addition of a small supercharger to the Stage 2 system.
One of the development quirks the car was left with was a front end that appears to sit very high, with an especially large space over the front tires. There are a couple of “legends” about why this happened, but the net result is that, in addition to the odd appearance, there is some poor front suspension geometry that leads to the front tires going toe-out at any suspension compression. This causes some rather strange handling as the car notoriously bump-steers.
See Photo 4.
In the early days of the car, owners developed what has been called the “chop and swap” upgrade. This consisted of relocating the front springs to the rear of the car, and taking the rear springs, cutting off one coil and re-installing them at the front. This, of course, led to a lower but stiffer front end and a lower but softer rear.
Better, but not optimal, and sometimes some odd noises could be heard at the front as the taper of the springs could not be maintained when being cut. There were some pretty extreme variations in how much to cut the front, leading some cars to appear excessively low.
See Photo 5.
In recent years, DeLorean Motor Company of Houston worked with Eibach to develop a quality replacement spring set that puts the car at the optimum ride height without resorting to such modifications. There are other aftermarket options for this as well.
There have been shock absorber options developed over the years involving modified aftermarket shocks that were intended for other applications. DMC Houston has offered a several custom shock designs from various European manufacturers. The current product is a set of shocks adjustable for height in the rear, with adjustable ride settings at both front and rear. There are also now adjustable lower control arms and stainless replacement components available.
See Photo 6.
In recent years, several vendors have come up with polyurethane suspension bushing parts to further stiffen up the suspension, although with all of these the owner must be careful as there are trade-offs in the areas of harshness and noise as bushings are made tighter.
It’s interesting to note that there is probably more development work going on now in enhancements to the DeLorean than at any time in the car’s history. This is driven by the continued interest in the car by enthusiasts who want to keep them on the road but don’t mind making them better.
Editor’s Note: All photos courtesy of David Swingle, DMC Midwest, except as noted.