Exige Power Recipe
Posted on 01 August 2015
Supercharged Exige/211 Power Recipe
by BOE Fabrication
This is a quick guide to getting the most power out of your factory supercharged Exige or 211 with just bolt on products. Further Driveline enhancements are not fully covered in this article, as the intention for this article is to address the most common questions as it relates to the basic power improvements for the Supercharged 2ZZ Lotus cars.
There are several ways to get more power out of the factory supercharged Lotus Exige with the 2ZZ-GE Engine
First evaluate your intended use and budget. We’ll recommend certain modifications for track cars that may not be as critical for street cars.
- Our Favorite Street Car and DE Recipe
- What Else for the Track?
A tune can make the single biggest difference in both absolute power and the delivery of the power. Don’t get into a big hurry to buy the tune until you have configured your hardware plans. The tune needs to be calibrated to work with certain hardware changes such as Injectors, Pulley, Fuel Delivery, Intake, and Exhaust. The BOE Torque 300 tune is configurable to just about any reasonable combination of power adders.
Only use intakes that are compatible with the tune you’re running. The stock airbox or TRD “Lotus Cup” air box are the basis for most aftermarket tunes. For the Exige that’s making best power it will max out the stock MAF housing found in those two air boxes. Tunes such as the BOE Torque300 can be configured with modified MAF tables in the tune to work with larger 3” MAF housing for more accurate fuel metering in the upper registers of the power-band. While this modification will not typically add a lot of power, it does make the throttle and power delivery smoother and safer on the bigger horsepower cars (275+ wheel horsepower). Please note, the only 3” MAF housing we configured for the Torque300 is made by us and available HERE.
The ExigeS and 220 models have a fuel pump that’s simply undersized and needs to be replaced. The Exige 240/260/Cup/211 have a larger pump, but is still marginal for the task. Preferred is a Walbro 255lph pump. These pumps are fairly easy to install with only a very slight modification to the pump housing to install. Alternatively, you can leave your stock pump in the tank and use a BOE Surge tank or similar that uses an external Walbro 255lph pump. This is all but required for track cars, as the surge tank will prevent fuel starve on the race track. For street cars, you have the option of adding the surge tank or replacing the stock pump. You do not need both. These are a highly recommended modification. Poor fuel delivery can result in failed motors.
The stock GREEN colored injectors are 440cc and are really undersized, but they can work. The Torque300 tune with a decent exhaust and 3” pulley will run the stock injectors static by 7500 RPMs or so. This is not a great situation. It is preferred to run a 525/550cc or 750cc injector. Injectors do not make more power. They do allow for correct fuel metering. The 525cc injector will supply more than enough fuel for any M62 Supercharged (the OEM Lotus supercharger) Lotus. There’s no need to run 750cc injectors on M62 powered cars. If you have a set that you want to run, check with your tuner first. A note about injector technology: RC injectors are Bosch EV-1 models and were developed in the 1970s. There are far better injectors that have been developed since the ‘70s that you should consider using such as Bosch EV6/EV14 and late model Densos. We prefer the Bosch EV-14s, but the Densos are good as well.
Pictures speak a thousand words. Campare the EV1 RC base injector to more modern Bosch Injectors. The lower mass of the new injectors helps to be more accurate, faster, and more reliable.
The stock Exige S intercooler is a tube and fine design. It's light-weight, but not particularly efficient. A bar-and-plate design is a good bit superior and that's what you should replace it with. Additionally, the lack of airflow to the intercooler is a big problem. Adding intercooler shroud ducts is important and makes a big difference. You can fashion your own or purchase kits in the aftermarket. For track cars and those looking for best performance, replacing the intercooler in addition to duct work is money well spent. The ReallyLightStuff intercooler is made by Bell and is a good, high flowing unit. We have our own intercooler using the same Bell core and several features that make it our preferred option over the RLS part. Ours is cheaper too! Check it out HERE. These Bell Intercoolers are a premium part and WILL free up power.
Mufflers. The stock Lotus Exige/211 mufflers are terribly restrictive. They must go. Any straight through muffler in the aftermarket will be a marked improvement in flow. We’re partial to our own “Featherweight” systems for various reasons, but from a power standpoint, most of the straight through systems are comparable from a power production point of view.
Headers. We have tested most of the aftermarket headers out there. 2bular, PPE, DMC, Larini, WeaponR, etc... They all will outperform the stock headers. We have found that the DMC header makes significantly more midrange torque than the others. We prefer to see a 1/2" thick flange, spring "ball and socket" type unions, and all stainless construction. Headers are absolutely worth the dollars. Check out our Header Shootout Here.
Catalysts. Contrary to popular belief, removing the catalyst on sub 300hp cars will not significantly impact the performance. However, there are reasons to remove the cat for off-highway use. We do NOT recommend catalysts for track use. The extended WOT running of the track, heat, etc will significantly reduce the catalyst life. "Hi Flow" or "Sport" cats often have stainless steel cores and will melt down on these cars very quickly. "Sport cats" will typically fail sniffer emissions tests as well. We recommend only cats with ceramic cores. Aftermarket catalysts do not seem to be any better than the stock unit and in most cases worse. All catalysts are bad for tuned header flow. There are no exceptions to this rule.
The stock supercharger is working harder than it was intended to with the stock pulley. This means that it’s not operating very efficiently. A smaller pulley will help to produce power, but don't get carried away. We recommend a 3” pulley and no smaller. These can be purchased HERE.
The faster you spin the blower, the harder it is to shed the additional heat and the more power the blower is taking from the motor via the drive belt. Therefore, effective intercooling becomes important to realize the impact of the smaller pully. For reference, the stock pulley is about 3.3 inches (82mm).
Below is a compressor map of the Lotus MP62 Supercharger. The area circled illustrates the typical operating range of this blower on the Lotus. You can see that this blower is not efficient in this range. Again, the smaller pulley will make power, but it is best utilized with a better intercooler and MUST be accompanied with a matching tune.
Things get more complicated with camshaft changes. Bigger cams require stiffer valve springs and stronger valves in addition to customer tuning. Contact us before swapping cams.
Our Favorite Street Car and DE track Recipe
With the above background, the following will make sense.
- Walbro 255 Fuel Pump
- BOE CAI
- BOE 550 EV-14 Injectors
- BOE HO 3" Pulley
- RLS Bell Intercooler
- DMC 4:1 Long Tube Header
- BOE ST Muffler
- BOE Torque 300 Tune to make it all work
An Exige/211 with the above combo will be a beastly car compared to anything stock. On a cool dyno run, you can see power numbers around 290whp (compared to 200-220whp stock!) with the above list without sacrificing any of the original drivability or reliability of the engine.
What Else for the Track?
That's a big question, because the list is truly infinite and really depends on your level of competition, budget, and frequency at the road course. At a minimum, if you're running slicks and other grip enhancers, a Surge Tank and intercooler cooler ducts should be on the list. At the higher power levels, the stock clutch will not be long for this world on the road course. We recommend the ACT HDSS found HERE, which is a great upgrade.