Why don't more turbo cars use CHARGECOOLERS?
Discussion
I believe this used to be a favorite of Lotus. Basically, instead of routing the air from turbo to intercooler to intake, a chargecooler cuts the potential lag by going straight from turbo to chargecooler to inttake across the top of the engine. The difference is that the air doesn't have to travel the circumferece of the hood to make it to the intake, and thus the response is better. It's also great for if there isn't a lot of airflow immediately near the turbo.
Of course, now it is not longer air/air, but air/water/air, if you will, and involves a pump and other doodads.
So why isn't this used more often nowdays?
Of course, now it is not longer air/air, but air/water/air, if you will, and involves a pump and other doodads.
So why isn't this used more often nowdays?
Good for the reasons that you stated, but less efficient, more to go wrong, power sapped by having to turn an extra pump. Plus you still need somewhere to site the rad for the cc.
Abbott did a charegcooler for the Saab c900 turbo as the intercooler doesn't see a lot of cold air (behind a headlamp). It's good but proves a bit unreliable when the power gets up towards 220bhp.
Abbott did a charegcooler for the Saab c900 turbo as the intercooler doesn't see a lot of cold air (behind a headlamp). It's good but proves a bit unreliable when the power gets up towards 220bhp.
t to go wrong, and again cost 
Herman Toothrot said:
Weight and layout, engine in front no point, big air flow through big front mount will alway be better than a charger cooler setup. Charge coolers are for setups where flow is limited and so a remote cooling rad is needed. Mid engined cas need charge coolers front engines don't.
My argument is that a proper chargecooler setup (yes, it will be more complex) should lower intake air temps effectively and also lower the lag by cutting down the distance from turbo to intake. Surely this can be advantageous?AUDIHenry said:
My argument is that a proper chargecooler setup (yes, it will be more complex) should lower intake air temps effectively and also lower the lag by cutting down the distance from turbo to intake. Surely this can be advantageous?
Lag is no longer a significant problem with a well-designed intercooled turbo installation. I'm barely aware that the engine in my Skoda is turbocharged; you've got to drive like a complete retard (like expecting it to pull hard on full throttle from 1200rpm) to make it show any signs of lag....so you're proposing a complex and costly solution to a problem that doesn't exist any more.
Sam_68 said:
AUDIHenry said:
My argument is that a proper chargecooler setup (yes, it will be more complex) should lower intake air temps effectively and also lower the lag by cutting down the distance from turbo to intake. Surely this can be advantageous?
Lag is no longer a significant problem with a well-designed intercooled turbo installation. I'm barely aware that the engine in my Skoda is turbocharged; you've got to drive like a complete retard (like expecting it to pull hard on full throttle from 1200rpm) to make it show any signs of lag....so you're proposing a complex and costly solution to a problem that doesn't exist any more.
Superhoop said:
Is that because of a well designed turbo/intercooler setup - Or because Skoda fit a variable geometry turbo? The latter I would think.
The turbo (whether it is variable geometry or not) is part of the turbo/intercooler set-up, surely?To be honest, I have absolutely no idea whether the VAG 2.0TFSi uses a variable geometry turbo, but if it does, presumably the bean-counters and engineers at VAG decided that this was a more efficient and cost-effective solution than chargecooling.
Whatever, no chargecooler, and lag isn't a problem...
Sam_68 said:
Superhoop said:
Is that because of a well designed turbo/intercooler setup - Or because Skoda fit a variable geometry turbo? The latter I would think.
The turbo (whether it is variable geometry or not) is part of the turbo/intercooler set-up, surely?To be honest, I have absolutely no idea whether the VAG 2.0TFSi uses a variable geometry turbo, but if it does, presumably the bean-counters and engineers at VAG decided that this was a more efficient and cost-effective solution than chargecooling.
Whatever, no chargecooler, and lag isn't a problem...
I would say it all comes down to cost & complexity.
Cost as in more parts and more time on the production line so they either take a bath on the margin or they have to up their price which when they are benchmarked against other makes higher price is not very palpable.
Complexity - yep more time to assemble, more R&D, more added servicing costs, more to go wrong, more weight.
Also whats the real end benefit? If there is none to very little then the customer will either want it for the same price or not go for that model due to imposssible to notice real world difference. Very similar to putting a bigger exhaust on a N/A car yep 5% more power - can you feel it... nope what you feel is the placevbo effect + you may also enjoy the louder noise.
Cost as in more parts and more time on the production line so they either take a bath on the margin or they have to up their price which when they are benchmarked against other makes higher price is not very palpable.
Complexity - yep more time to assemble, more R&D, more added servicing costs, more to go wrong, more weight.
Also whats the real end benefit? If there is none to very little then the customer will either want it for the same price or not go for that model due to imposssible to notice real world difference. Very similar to putting a bigger exhaust on a N/A car yep 5% more power - can you feel it... nope what you feel is the placevbo effect + you may also enjoy the louder noise.
Superhoop said:
Sam_68 said:
AUDIHenry said:
My argument is that a proper chargecooler setup (yes, it will be more complex) should lower intake air temps effectively and also lower the lag by cutting down the distance from turbo to intake. Surely this can be advantageous?
Lag is no longer a significant problem with a well-designed intercooled turbo installation. I'm barely aware that the engine in my Skoda is turbocharged; you've got to drive like a complete retard (like expecting it to pull hard on full throttle from 1200rpm) to make it show any signs of lag....so you're proposing a complex and costly solution to a problem that doesn't exist any more.
Anyway, 1200 rpm is probably below the boost threshold so not lag.
AUDIHenry said:
I used to run a VAG 2.0T in my Audi and I can say that lag was a problem until about 2500ish, before which time not very much is happening. It is curious that we can drive a car with the same engine and reach two different conclusions.
Perhaps they've revised the engine management?Busa_Rush said:
Anyway, 1200 rpm is probably below the boost threshold so not lag.
Yes, you're right. Perhaps I should have said that it's only when you expect the engine to pull from that sort of rev range that the turbo becomes intrusive, rather than shows any sign of lag; lag is technically the wrong word. It's the surge in power as the turbo spools up which is noticeable if you give it big throttle at such low revs(I was going to say 'at large throttle openings', but since it's a fly-by-wire throttle, presumably foot-to-the-floor doesn't necessarily equal a full open throttle unless the engine management allows it?)Certainly by the time it's at the 2,500rpm range mentioned by AudiHenry, the power curve is fairly seamless and lag-free.
And accelerating from idle is similarly smooth and seamless provided you don't just floor the throttle (but then, being used to small, highly-strung nat. asp. engines with carburettors, such behaviour is completely alien to me, anyway).
to answer the question properly...
Water based coolers cost money and add complexity, so no OEM is going to go this route unless it's got issues with a simple FMIC
classic example is the old Subaru Leggacy 4cam turbo, that was water intercooled, however, when they brought the Impreza out, they went for a simple air to air ontop of the engine, it never worked as well and had to have water sprays etc fitted, but cost much less to make.
for 99% of cars out there, a simple FMIC works well enough, OEM cars do not run much boost, so they actually have little heat-load to shift - that said, some dismals run woefully small intercoolers.
for a mid-engined setup, air to air just does not work, you either have to re-design the bodywork for some HUGE air-scoops in a vain attempt at getting some air though the intercooler rads, or live with them just not working - see Nobles for examples of this.
other considerations are the total airpath volume (somebody has already mentioned this), even with trick turbo's etc, it's still an issue you could do without, also when the car is not moving, the intercooler is doing nothing but heat-soaking, a water based intercooler system has significat heat capacity in the water, thus you have a huge thermal damper in the system, it can still cool when stationary, and will cool the water down when the car is moving all the time, not just when the throttle is open.
Water based coolers cost money and add complexity, so no OEM is going to go this route unless it's got issues with a simple FMIC
classic example is the old Subaru Leggacy 4cam turbo, that was water intercooled, however, when they brought the Impreza out, they went for a simple air to air ontop of the engine, it never worked as well and had to have water sprays etc fitted, but cost much less to make.
for 99% of cars out there, a simple FMIC works well enough, OEM cars do not run much boost, so they actually have little heat-load to shift - that said, some dismals run woefully small intercoolers.
for a mid-engined setup, air to air just does not work, you either have to re-design the bodywork for some HUGE air-scoops in a vain attempt at getting some air though the intercooler rads, or live with them just not working - see Nobles for examples of this.
other considerations are the total airpath volume (somebody has already mentioned this), even with trick turbo's etc, it's still an issue you could do without, also when the car is not moving, the intercooler is doing nothing but heat-soaking, a water based intercooler system has significat heat capacity in the water, thus you have a huge thermal damper in the system, it can still cool when stationary, and will cool the water down when the car is moving all the time, not just when the throttle is open.
My GT-Four used to have one but I ditched it in favour of an FMIC. one guy replaced the charge cooler with an FMIC with back to back dyno runs and increased power by something like 20BHP, not sure if the GT-four has a particularly bad setup but intake temps are noticeably (?sp?) higher with the CC than FMIC.
AUDIHenry said:
Sam_68 said:
Superhoop said:
Is that because of a well designed turbo/intercooler setup - Or because Skoda fit a variable geometry turbo? The latter I would think.
The turbo (whether it is variable geometry or not) is part of the turbo/intercooler set-up, surely?To be honest, I have absolutely no idea whether the VAG 2.0TFSi uses a variable geometry turbo, but if it does, presumably the bean-counters and engineers at VAG decided that this was a more efficient and cost-effective solution than chargecooling.
Whatever, no chargecooler, and lag isn't a problem...
Lag is when your doing say 4000rpm and then stamp on the throttle, lags the time it takes for boost target to be hit.
Boost threshold is the point in the rev range you start to get boost.
i.e. my mx5 doesn't really produce any significant boost until 4000rpm but when operating above 4000rpm which it always is on track there is no lag thanks to the ball bearing turbo.
eybic said:
My GT-Four used to have one but I ditched it in favour of an FMIC. one guy replaced the charge cooler with an FMIC with back to back dyno runs and increased power by something like 20BHP, not sure if the GT-four has a particularly bad setup but intake temps are noticeably (?sp?) higher with the CC than FMIC.
And people put the GT4 charge coolers on the MR2 as you can't get good airflow through an intercooler on the MR2.Its all about available airflow.
If you accept that no thermal transfer is ever 100% efficient, you will understand why a chargecooler is less efficient than an intercooler (all other things being equal).
Ignoring the complexity and weight (not particularly complex or heavy IMO) – the main issue is that you have an inefficiency getting the hot charge air into the water and then another inefficiency getting the hot water cooled down by the ambient air.
Chargecoolers are selected usually to solve packaging issues, not efficiency issues. Lotus used them because they couldn’t run charge pipes to the front of the car for a normal FMIC for example.
The only time a chargecooler has a short-term benefit over an intercooler, is for drag-racing – because you can fill the tank up with ice and achieve very low inlet temperatures.
In my experience 10 seconds of boost, would take about 3 miles of non boosted driving to recover from – I tried massive pumps, tanks of water, huge radiators etc etc – with varying success. With an intercooler, it recovers instantly.
If you’re bored, you can read through my 8 pages (and 3 years) work of intercooler work here
http://www.mez.co.uk/turbo8.html
Suffice to say, I’ve replaced it with an intercooler now – which just “works”
Ignoring the complexity and weight (not particularly complex or heavy IMO) – the main issue is that you have an inefficiency getting the hot charge air into the water and then another inefficiency getting the hot water cooled down by the ambient air.
Chargecoolers are selected usually to solve packaging issues, not efficiency issues. Lotus used them because they couldn’t run charge pipes to the front of the car for a normal FMIC for example.
The only time a chargecooler has a short-term benefit over an intercooler, is for drag-racing – because you can fill the tank up with ice and achieve very low inlet temperatures.
In my experience 10 seconds of boost, would take about 3 miles of non boosted driving to recover from – I tried massive pumps, tanks of water, huge radiators etc etc – with varying success. With an intercooler, it recovers instantly.
If you’re bored, you can read through my 8 pages (and 3 years) work of intercooler work here
http://www.mez.co.uk/turbo8.html
Suffice to say, I’ve replaced it with an intercooler now – which just “works”
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