Intercooling with proper engine management should be a wash.

 

That's an interesting question. I'd say that, everything else being unchanged ie pistons, bearings, etc, it's #2. Just adding the intercooler would tend to reduce engine life because the engine would be generating more power thus more stress on internal components.

One way to rationalize/reconcile R&B's claim would be that after adding the intercooler you change your driving technique (lighter right foot) to where you never exceed the non-intercooled 350 BHP rating, then in theory engine life could be enhanced. But that would never happen, otherwise why bother installing the intercooler? 😆

 

hmmm - OK in real world driving though the IAT would be lower overall avg. Especially on hot days with extended driving. Wouldn't a cooler engine have a longer life? In a race car yeah - more power so shorter life. Also trying to flog a heat soaked engine seems like it would be worse than flogging one with good IAT. Or, in the last scenario, would the computer just shut the power down so you would not be getting nearly as much out of it?

 

It's post #3. Adding intercooling will allow more boost for longer periods of time putting more stress on the motor but providing more power. Because of the engine management system, just installing an intercooler you cannot get full advantage unless you can modify the ECU to utilize the full benefits of the intercooler. Because Lotus engineered the sh-t out of everything to take full advantage of everything, there is less "reserve" meaning if you try get much more out of the motor you get very close (probably too close) to over-stressing the motor. Especially considering the age of the motor and all the Ethanol in today's fuel. For all the effort and cost to add intercoolers, IMHO it isn't worth it. My advice would be, if a Lotus isn't enough car for you, maybe you should look for another car with more power.
David Teitelbaum

 

That does raise another question. If one were inclined to install the intercooler (some folks like to re-engineer their rides, beyond just the pure performance gains) then is there an ECU tune available to maximize the intercooler benefits?

 

As far as the 918 V8 engine itself everything I've seen is that it can easily accomodate a substantial power increase. As I understand it the primary reason it was tuned to 350 BHP in the Esprit was that Lotus was not going to change the Renault gearbox, and that was/is the weak link in the powertrain.

The block is engineered with cross-bolted 6-bolt main bearing caps, baffled sump is cast aluminum, both contributing to a stiff sturdy foundation structure. Valve actuation is direct, ie minimal moving parts.

Lotus published specs indicated power levels of 350 HP turbocharged (as delivered in the Esprit), 420 HP intercooled, 530 HP racing (restricted version, this is what competed in GT1, outpacing McLaren F1 GTR's and Ferrari F40's), and 600 HP racing (unrestricted version).

Certainly internal mods are required for the higher power levels - eg forged pistons, maybe upgraded con rods, bearings, valves etc - but that's true with any engine that is modified to produce more power.

Side note: the 530 HP GT1 Esprit used a single turbocharger with intercooler. Don't think I heard of any engine failures despite the fact they were outrunning 600+ HP McLarens. Primary reliability issues for the Esprit were brakes, gearbox (Hewland sourced), and electrical.

 

Thanks for putting up the brochure of the 918 engine. Nice item to have in real. The designers already anticipated charge cooling.

@David. No I am definitely not interested in more power only higher reliability of the engine. Maximum speed in The Netherlands is 100 km/h. However, I am planning to take the car out on long trips through Europe (>2000 km) and I just want to minimise the chance of getting stranded. I got a bit worried when I read the Ramspott & Brandt advertisement that says:

'After intensive development work we designed an air/water chargecooling system for the V8 engine, similar to the 4cyl. Esprit. This system improves the durability of the V8 engine by reducing critical intake air temperatures. A non chargecooled Esprit V8 reaches such a high intake air temperature that the firing temperature in the combustion chamber exceeds critical values. As a result there will be a malfunction of the pistons or the liners. With our new chargecooling system the intake air temperature will be reduced about 60 percent. It does not exceed 45 degrees celsius at a speed of 270 kph. The engine power increases from 354 up to 405 BHP (with red race ECU and a boost of 0,85 bar it could even reach 500 BHP).

My conclusion based on your answers thus far is that 'ceteris paribus' a charge cooled engine improves reliability but as soon as you take advantage of the extra power possible due to the charge cooling and accessible with a tuned ECU, the reliability goes down again. I always keep in mind that the relationship between extra power and engine wear is exponential and not linear. I do not need extra power so I am not going down the charge cooling route which leaves me with one more question which is ... what is the effect of the smaller diameter cooling pump pulley that according to Ramspott & Brandt improves the cooling capacity especially at idle and lower rpm. No drawbacks for the other components driven by the serpentine belt or the belt itself? This seems so simple and obvious that it is hard to imagine that Lotus didn't think of it themselves.

 

Great question on the pulley. I think "easy" upgrades like a smaller pulley, that were not originally done by the OEM are often related to emissions, noise, cost or gas mileage (related to emissions).

In this case I wonder if the reason is not emissions, motors have peak combustion efficiency when they are warm and (I think) the hotter the better. Sometimes to the detriment of engine health (all stuff I read on the internet so ,,,,). This is related to why manufacturers have all sorts of tricks to get motors to warm up more quickly - less emissions. IIRC the back pressure valve on the S4 Esprit was for there for this reason, faster warm up to get to lower emissions (unburned fuel).

I have seen upgrades available for the cooling systems on many enthusiast cars over the years that help the motor run cooler in normal driving, many times this includes changing the thermostat to open earlier for example.

Also, gas mileage, turning the water pump faster = more drag = more fuel burned.

 

Interesting that they offer this pulley, wasn't aware of it. It's pretty simple I guess, a smaller pulley will spin the water pump faster thus, in theory, more coolant flow at a given RPM.

Does this make the engine run cooler? I would say, "it depends." Pushing more coolant through the system might make the engine run cooler. But with faster flow that means the coolant is spending less time in the radiator so it might not be transferring as much heat, thus negating the desired effect. At lower RPM's maybe the effect is minimal and there is in fact more cooling, but at higher RPMs this faster flow could become an issue. At the same time more engine power is being used to move this larger qty of coolant, so there's a touch less available to accelerate the car. But that's probably negligible, doubt that the small power loss would be felt.

From an empirical standpoint I have seen that RPM definitely affects cooling. My car will run all day at medium to highway speeds in >95F (35C) ambient conditions and the engine temp rarely goes above 90C or so, usually it's cooler than that. But if it has to idle for any length of time it will get to 100C, maybe a touch higher at times.

Is this a problem? No it isn't, the cooling fans kick in and keep it well within a safe range. Per the owners manual (see below) this is exactly the way the system is designed to function. Further, it indicates that the critical temp is 120C since the proper coolant mixture combined with the pressurized system doesn't boil until above that point, at which time the gauge cluster warning lamp would illuminate. Although I'd be pretty nervous if my temps ever got anywhere near this range, which thankfully they don't. The manual stipulates that temps over 100C while idling need not be of concern, as long as they stay below the critical point.

Bottom line my feeling is the Lotus engineers probably did extensive testing when they developed the V8 and sized the water pump pulley for an optimal cooling balance between low and high speed motoring, and minimal parasitic power loss. Has R&B's pulley been through the same testing process? Do they present any data about the cooling effects at low and high speeds in various ambient temps?

If you have a cooling issue my advice would be take the usual steps ie flush the system, ensure proper coolant mixture, clean radiator debris, etc. Easier and less risky than trying to replace the pump pulley. But if you do move forward with the pulley replacement please post the results, I'm sure they would be of interest to all V8 owners.

 

I wonder if R and B found the pulley was a needed/ a benefit when the CC system is added? More volume, more losses as it goes through radiators, pipes and bends. Maybe the CC are more efficient when the coolant is moving a little faster to the possible detriment of the radiators as mentioned above. All speculation - fun to think about.

 

Please Google the 'Too much coolant flow myth'. Equation for heat transfer indicates that increased flow rate increases heat transfer. There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a Constant (the specific heat of water) times the Delta T (fluid temp out minus fluid temp in) : Q = M x C x Delta T

 

Hmmm I would of thought there was a part of that equation related to the efficiency of the radiator. But - from my experience I have seen where removing the T stat all together will cause the engine to never reach operating temp. So I think that fits in with that equation. I think you should add the pulley at next t belt change and see if you can see a difference on the gauge.

 

I got a bit worried when I read the Ramspott & Brandt advertisement that says:

A non chargecooled Esprit V8 reaches such a high intake air temperature that the firing temperature in the combustion chamber exceeds critical values. As a result there will be a malfunction of the pistons or the liners.

The greatest marketing tool across any industry is FUDD (Fear, Uncertainty, Doubt & Despair). Lotus wouldn't design the engine with these parameters, sans intercooling if it was going to pose short or long term issues. That said... intercooling an engine to return the same power output levels will definitely allow it to run cooler intake temps, and the lower, denser charge should, in theory, extend component life. Or, give a mild increase in power that trades off the benefits of the cooler intake temps with the detriments of more mechanical force on the bearings and reciprocating parts.

what is the effect of the smaller diameter cooling pump pulley that according to Ramspott & Brandt improves the cooling capacity especially at idle and lower rpm. No drawbacks for the other components driven by the serpentine belt or the belt itself? This seems so simple and obvious that it is hard to imagine that Lotus didn't think of it themselves.

Higher volumetric flow will definitely pull the heat away quicker, internally. The heat delta across the hot components, under the same testing and power conditions, would essentially be a constant when comparing the two set-ups. Thus, the increased flow will move that heat away at a quicker rate, as the volume of coolant across the components is faster, circulating back to the rads to cool it back down sooner as well. The efficiency of the rads with the thermostat open would determine how effective the pulley would be on the overall heat dissipation of the system. As mentioned previously, Lotus has a tendency to use components that, nearing the performance limits, are already near or at max efficiency and as such, improving the efficiency of one component, may be rendered moot if another component downstream can no longer perform any better because it has already reached its max design capabilities. Not sure how efficient the Esprit stock rads are, though many folks are at the point where replacements and re-cores are occuring. Speeding up the coolant pump, at some point, will cause cavitation. It's unavoidable with a rotating pump. Again, not sure what the point of cavitation is with our coolant pumps, though I'm sure Lotus used a pump that wouldn't cavitate at high temps and rotational velocities consistent with the 7000-7200 rpm limits on the various factory ECUs.

 

I think they are hinting at predetonation (or knock) with higher intake temps. Also, radiator efficiency doesn't really account for needing radiator replacements after 20 years. That's more of a maintenance issue.

 

Also, radiator efficiency doesn't really account for needing radiator replacements after 20 years.

Correct - I wasn't very clear. I was implying one could possibly go with a more efficient design as it seems many of the original rads are beginning to come out for one reason or another at this point. But with the mounting angle and already tight quarters, I'm not sure how much better the cooling could actually get.

 

As to the original post, (#1). I would think that a lower IAT is kinder to the engine regardless of use, and should enhance engine life and provide some extra tolerance for bad gas or extreme conditions. Maybe a bit more efficient as well. But, for the intended use as a touring car it would not be worth the bother, expense and loss of trunk space.

(#2) would come into play more once one was tuning to take advantage of the cooler IAT's