Sorry I can't hit every board every day. This is a REAL good question and one that EVERY Saturn sales consultant should be able to answer and currently can’t for shit.
Now lets see if I can do this in fewer than 1000 words.
First of all the GM Racing program started with a 2.2L ECOTEC (L61) motor designed to only make a maximum of 150 HP ever. The LSJ is a motor that is designed to make 300 HP in production form and currently only makes 210 HP in the SAAB 93T and 205 in the Saturn RedLine. While the main structure of the LSJ and L61 are the same; the way they are made, the materials used and a few upgrades necessary for boosted motors make the LSJ an even better motor than the L61 already is. Through the extreme testing GM did for the Sport Compact race program they discovered a few limitations of the L61 along with normal production factors that showed up over the course of the first few years in L series vehicles.
The LSJ and SAAB 93 use the same motor and it includes all of the production upgrades made from findings both from GM Racing and through the first few years in the L series. The four-valve, overhead cam engines deliver excellent fuel economy and low emissions in a dependable, durable package with low noise and vibration. The Ecotec 2.0L SC incorporates a number of components from the proven Saab 2.0L design, including a direct-mount oil cooler, oil jets for piston cooling, heavy duty pistons, stronger connecting rods, forged steel crankshaft, larger oil sump, sodium-filled exhaust valves for improved durability, and a high-strength aluminum cylinder head. – GM Media Information
GM Racing found that the head tended to deform around 400 HP so they pre-loaded the #1 and #4 cylinders through the head with support braces in the early race heads and later had production updated with webbing to do the same. Through production it was found that the lost foam casting process can have instances of voids in the casts which would lead to waste castings or if not found in time a potential motor problem down the road. Sand casting didn’t have the same issues and provided a denser overall cast so along with the webbing the SAAB and LSJ motor uses a sand cast head assembly.
From what I understand all production heads now have the additional webbing and that includes the GM performance products heads.
It’s common knowledge that 86mm bore x 86mm stroke is the perfect size and shape of a 4 cylinder motor when working with high power forced induction motors. Most of the sport compact drag race vehicles all run this ‘square’ configuration or one very close to it. Some programs go a little over or under to address rod to stroke ratio and how it affects turbo spool-up, but in general this is the “golden square” of 4 cylinder motors. Lot’s of testing has been done for many years on combustion in relation to power produced, detonation, heat, loads, ect. and it has always been found that a bore of 86 mm results in an almost perfect combustion chamber size in every aspect important to motor operation and efficiency.
When you address the details in how this very well designed and built motor is force fed it quickly becomes clear where the lines are drawn. While the ultimate top end power will always go to the centrifugal compressor it’s not uncommon for the life of a roots style blower to last many times that of any turbo. As a manufacture failure rate is important and even in limited run vehicles as low as 5000 in the case of the 2004 RedLine GM considered that when picking a proven roots blower over a Turbo. GM has a long and solid history of proven performance and longevity in roots blowers many of which are being used today in sport compacts as a second life from pick-a-part kits. Now I’m not saying that they don’t fail, but as a function of them not being linked to the engine cooling or lubrication system in the rare event they do fail it can’t impact the life of the engine through contamination. A turbo failure rate while also rare does happen more often and sooner than a roots blower and when it does it can cause problems with both engine cooling and lubrication since both systems are routed directly through the turbo.
Even when it comes to just mechanical limitations of each type of system the limits are defined by normal failure rates and magnified by enhancements to the vehicles. In each case a motor can only take so much of a load before it will begin to fail and I think it’s safe to assume 300 HP is a safe limit and 350 HP is the maximum limit. How that plays into things with the RedLine and the SRT-4 is that the M62 blower can’t even move the necessary volume of air to exceed 275 HP let alone 300 so you can forget 350. The SRT-4 on the other hand can inexpensively be modified to increase boost pressure resulting in more air volume and eventually a larger displacement compressor for much less that it would cost to replace the roots blower on the RedLine. In contrast though you could spend as much for a SRT-4 upgrade package as it would be to install a Turbo system on top of the roots blower in the RedLine resulting in the same final result; more power available than the motor can handle. The next progressive step would be internal modification in which case I can only say the RedLine wins hands down based on my time with both engines, but NO one wants to believe. GM racing REALLY does use all stock internals other than the pistons, rods and crank. All the bearings, pumps and many of the valve components are solid as a rock up to the 800 HP mark. With the LSJ motor having a forged crank that is stronger than the L61 crank GM replaced in testing it’s likely that the LSJ crank will withstand HP production close to 800 HP and beyond. Since anything over 500 HP is beyond the limits of any streetable FWD vehicle and PCM control it’s not a real factor. So for the $1000 MAX in pistons and rods, $100 for copper head gasket and a measurable amount of DIY work you have a 500 HP LSJ motor that would probably last 50,000-75,000 miles with proper tuning.
By that time I would just go turbo all the way, but swapping out a S/C for a Turbo in the beginning makes this whole discussion a moot point doesn’t it?
I mean let’s be honest take away the forced induction in both vehicles and what do you have left? A new 2000 delta platform Saturn ION Quad Coupe, with a sport suspension and the seats people have been asking for going on 13 years now and the same old Neon no one liked 5 years ago.
Bottom line: You remove all the power adders that increase the vehicle complexity, chance of failure, and dealer difficulty and you are left with a simple decision.
Saturn, Honda/Acura, Toyota, VW, Subaru, Mitsubishi, Nissan, Hyundai, Dodge, Ford
All the V6s are overweight wastes of time in most cases and all the N/A 4 cylinders are at the limit of power. The Turbo and S/C are the only baseline starting points.
The fact that a S/C will outlast a Turbo any day of the week just adds to the quality GM is offering in the RedLine.