The Lotus Cars Community banner

1 - 18 of 18 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter #1
ok...here is the low down. 2000 lotus v8 new turbos, new iradium plugs, dual bov(sound awesome) and now stage 2 chip from p.u.k. My question is at what psi should one start thinking of liquid intercooling. I found this web site that sells the same liquid intercoolers(just not painted lotus engine red) for $150 each. Or one intercooler, small radiator, fan and pump for like $279. YOU can also add a ice box for $99. :clap: The website is Intercooler Pipe Fabrication - Silicone Intake Systems Auto Parts check it out and tell me if i am wrong. I just think that it would help with temps, longivity of the engine and looks awesome.
 

·
Registered
Joined
·
2,309 Posts
...
My question is at what psi should one start thinking of liquid intercooling.
...
It is really more of using an air to air intercooler when you have steady state conditions as they probably move more heat, and have less parts.

The Air->Water>-Air are good when the engine is not aways at WOT, as the water has a lot of heat capacity and buffers the system.

Also when the engine is a long way from the intercooler, then for an engine that varies the load the a-w-a does not require the long of piping to more air to the front and back.

So it is more a case of intercooling or not, and then whether you do water or non-water based.
 

·
Registered
Joined
·
284 Posts
The Esprit will benifit from intercooling at almost any boost level. Even with stock boost levels the ECU will take defensive measures, reducing timing advance and boost levels. The question is the expense and loss of trunk space. The cheap products from the web site you referenced are all made in China and have signifiant pressure drop across the intercooler, requiring more boost and resulting heat. I have measured IAT levels of 220 *F. on a hot day on the track, with stock boost levels. Real effective intercooling can confuse the ECU into setting insufficient EGR flow errors, as the IAT is reduced and the ECU uses temperatrure to deterime effective EGR flow.
 

·
Registered
Joined
·
935 Posts
re: BOV

BOV protects the intercooler, engine and the turbo. If you are on full boost and suddenly close the throttle, as in the light changing on you, approaching a corner at the track etc., the air suddenly has nowhere to go. The turbo has inertia and is stillturning at full speed. The throttle is closed and the pressurized air is trapped. If the BOV does not open and release all that air,m the follwing will happen:

1. There is a pressure spike and, it may burst the intercooler. The intercooler is usually the weakest link.
2. The same pressure spike may get to the engine and cause detonation or the car will actually feel like it speeds up when you apply the brakes.
3. The air may surge and so bad things to the engine. This is not likely with modern engines.
4. The air will try to reverse through the turbo and back out again. This can do much damage. It puts a lot of stress on compressor blades and may rip them off. It puts a lot of stress on turbo bearings. It causes turbo surge that does more of the same.
5. The turbo will suddenly decelerate to the appropriate speed, so when you hit the gas again, as after apexing a corner at the track, you will have excessive turbo lag.

So, a BOV is a very simple and useful fevice.

It is just a valve on a diaphragm with one side connected after the throttle and theother before. The pressure differential across the throttle (which only happens when it is significantly closed) opens the BOV, and bleeds off boost.

If your cas has a MAF, BOV to atmosphere will cause a rich condition, since the MAF thinks all that air went into the engine. REcirculating BOV's put the air back in front of the turbo but behind the MAF. This has an added benefit of keeping the turbo spooled up, but the plumbing is more complex. Also, the satisfying BOV sound cannot be heard!

Anton

How does a BOV sound? Any real benefit to BOVs? How is "blow off" managed on a stock Esprit V8?
 

·
Registered
Joined
·
671 Posts
Please note my corrections below. This isn't meant to be a flame on Anton, but accurate information is my goal. Having worked on turbocharged cars for more than 20 years in addition to being a trained heavy wheeled vehicle mechanic in the USArmy, these specifics are very important to understanding certain aspects of turbcharging and physics of the system.

BOV protects the intercooler, engine and the turbo. If you are on full boost and suddenly close the throttle, as in the light changing on you, approaching a corner at the track etc., the air suddenly has nowhere to go. The turbo has inertia and is stillturning at full speed. The throttle is closed and the pressurized air is trapped. If the BOV does not open and release all that air,m the follwing will happen:

1. There is a pressure spike and, it may burst the intercooler. The intercooler is usually the weakest link.

Unless you have a very poorly designed plastic or rubber intercooler, a V8 with T28 or even T25 turbos will not burst an intercooler, perhaps a coupling may blow off due to a bad clamp, but you're not going to blow an intercooler up if it is of sound design

2. The same pressure spike may get to the engine and cause detonation or the car will actually feel like it speeds up when you apply the brakes.

The throttle plates are closed and thus the boost is trapped between the spinning turbo inducer and the throttle plate, thereby effectively inactivating it's ability to get "into" the engine and cause detonation. Sorry.
3. The air may surge and so bad things to the engine. This is not likely with modern engines.

This one you actually have right! The surge against the delicate compressor wheel can cause the pressure waves to revert back into the turbo's inducer housing and bend or damage the "fan" blades or "vanes" as they are known to fail or worse, make contact with the inducer(compressor) housing and seize or chip off a piece. This will do the most damage in a non-BOV equipped vehicle. HOWEVER, the boost levels used within the Esprit even with a tuned/modified ECU is not likely to cause harm.
4. The air will try to reverse through the turbo and back out again. This can do much damage. It puts a lot of stress on compressor blades and may rip them off. It puts a lot of stress on turbo bearings. It causes turbo surge that does more of the same.

See #3
5. The turbo will suddenly decelerate to the appropriate speed, so when you hit the gas again, as after apexing a corner at the track, you will have excessive turbo lag.

The BOV used correctly will maintain the current turbo speed(100,000rpm or so) and thus when the throttle plate opens again, you will resume boost more quickly and have less lag as you reapply throttle
So, a BOV is a very simple and useful fevice.

It is just a valve on a diaphragm with one side connected after the throttle and theother before. The pressure differential across the throttle (which only happens when it is significantly closed) opens the BOV, and bleeds off boost.

If your cas has a MAF, BOV to atmosphere will cause a rich condition, since the MAF thinks all that air went into the engine. REcirculating BOV's put the air back in front of the turbo but behind the MAF. This has an added benefit of keeping the turbo spooled up, but the plumbing is more complex. Also, the satisfying BOV sound cannot be heard!

Anton
 

·
Registered
Joined
·
667 Posts
As for what the blow-off valves sound like, there is a release of air when you lift off of the throttle. The valves by the company "HKS" can be heard in these videos on the V8 Esprit:


Not everyone likes the sound, but personally I love it. Let's me know that the turbos are working and provides another unique aspect about the car.

JAE sells the HKS bovs along with the necessary intake pipes with the adapters welded on. The stock EGR valve needs to get moved, but otherwise it sounds like a relatively easy install.
 

·
Registered
Joined
·
3,135 Posts
Besides all of the bad things that may or may not happen, the intercoolers by themselves won't do all that much. The ECU isn't going to allow for the full effect to be realized. Besides, on the Lotus V-8 you are not in boost all that much unless you are tracking the car. At the boost levels you run on a stock V-8 the BOV valves are not necessary but for many they sound "cool". As for longevity, if using the intercoolers allow you to increase boost any significant amount, the engine will not last very long. Same bad news for the transaxle. The drivetrain is already running near it's upper limits, any additional power you manage to get will be at the expense of it's longevity. IMHO if the Lotus V-8 is not enough car for you, you might want to consider getting another, different car that you can flog. It will probably be cheaper in the end. Lotus parts are expensive, especially for the V-8.
David Teitelbaum
 

·
Registered
Joined
·
320 Posts
I agree with David 100% , in fact I would not have even done the modifications you have already carried out.

A few years ago I was very interested in buying a V8 Esprit , but the fact is it is already a highly stressed car and the modifications that most of the cars I saw for sale that I could afford had done to them were at the expense of outright reliability, and as I didnt want to be messing with the thing constantly I opted for a more bulletproof British performance car.
 

·
Registered
Joined
·
4,852 Posts
If your cas has a MAF, BOV to atmosphere will cause a rich condition, since the MAF thinks all that air went into the engine. REcirculating BOV's put the air back in front of the turbo but behind the MAF. This has an added benefit of keeping the turbo spooled up, but the plumbing is more complex. Also, the satisfying BOV sound cannot be heard!

Anton
Esprit is a MAP system, not MAF, so re-circulation is not necessary. Though I would recirc a BOV, since I hate that "pssshhhh" sound.
 

·
Registered
Joined
·
4,852 Posts
Intercooling doesn't just add power, it can greatly cool your intake temps. IIRC the normal MAT temps for a V8 turbo should be around 214F on say a 90deg day.

Here are my intake temps with boost on a 90F day (Esprit SE air to water intercooler with an electric high volume pump), temps are in C (46C =115F)
 

·
Registered
Joined
·
394 Posts
Esprit is a MAP system, not MAF, so re-circulation is not necessary. Though I would recirc a BOV, since I hate that "pssshhhh" sound.
What effect does taking the heated compressed air being vented from the BOV and feeding it to the turbo inlet to be re-heated over again do to the effective termerature of the intake charge right after you finish the shift and get back on the throttle?

Knut
 

·
Registered
Joined
·
4,852 Posts
With the intercooled engine's intake temps being not too much above ambient, and the small momentary volume of slightly warmer air... shouldn't be much effect at all. Definitely not worth worrying about compared to the increase in throttle response.

If the BOV is mounted after the secondary injectors (on the 4cyl SE this is easy) then you actually have fuel mixed in as well (would definitely recirc in that case!).

Similar to this (sorry 4cyl again, not sure this is feasible on the V8).
the intercooler on the left, and the BOV mounted on the lower right of the common mixing plenum, downstream from the secondary injectors. This method can obviously make the car a little rich for that moment after the BOV opens... Better than lean.

 

·
Registered
Joined
·
394 Posts
I wasn't questioning the benefits of a BOV setup (I have BOVs on my own V8 Esprit and it works great to keep me on the bost when shifting) and I was only asking about the wisdom of venting heated air into the turbo inlets on a V8 (where there aren't intercoolers). If the compressed air temps are in the 200F range, then venting that into the inlet would seem to be like driving the car on a 200F degree day. If the sound of venting to atmosphere is annoying, then replacing the trumpet on some of the BOVs with a muffler might be an alternative to consider.

On the V8 the BOV setup is usually ahead of the throttle plates where there is no fuel added to the mixture yet. Is it a good idea to run an air/fuel mixture through a hot turbo like you imply? Of course venting a fuel/air mixture probably isn't much safer.

Knut



With the intercooled engine's intake temps being not too much above ambient, and the small momentary volume of slightly warmer air... shouldn't be much effect at all. Definitely not worth worrying about compared to the increase in throttle response.

If the BOV is mounted after the secondary injectors (on the 4cyl SE this is easy) then you actually have fuel mixed in as well (would definitely recirc in that case!).

Similar to this (sorry 4cyl again, not sure this is feasible on the V8).
the intercooler on the left, and the BOV mounted on the lower right of the common mixing plenum, downstream from the secondary injectors. This method can obviously make the car a little rich for that moment after the BOV opens... Better than lean.
 

·
Registered
Joined
·
671 Posts
Correct me if I'm wrong, but once throttle position drops below a certain threshold, don't the secondary injectors shut down? I ask only because I have my BOV mounted on my plenum in a similar configuration. I have never had any issues with the BOV venting extra fuel into or onto my engine. I have the crankcase vent to atmosphere with a small K&N filter on it so there isn't any vapor ingested by the engine, although it sure makes a mess on my lower chassis frame rail!
 

·
Registered
Joined
·
935 Posts
BOV re-circulation

I am not an expert on Lotus 4 and V8 turbo set-up. So here are some general facts about re-circulating.

1. If you have an intercooler the re-circulation works like and air conditioner and re-circulated air can be colder than original intake. On re-circulation the air will expand (pressure drop back to atmospheric) and cool down. If there is no intercooler it will not cool down back to original temperature, since the compressor is less than ideal adiabatic compressor. The temperature rise will be much less than you think, but the slight pressurization of the compressor intake due to extra avaialble air will keep it spinning so much faster...

2. If you have MAF or secondary injectors, you must re-circulate. Bad things and engine fires may happen.

3. I noticed an interesting artifact of some BOV valves. If the engine is at light cruize or near idle and the throttle is snapped shut, it may produce enough of a pressure differential on the BOV valve that together with internal engine vacuum will pull it slightly open. At this point it will tend to suck-in unflitered air! Some BOV's have filters on them. Recirculation will suck-in filtered air, in any case. So it is much safer!

Anton


What effect does taking the heated compressed air being vented from the BOV and feeding it to the turbo inlet to be re-heated over again do to the effective termerature of the intake charge right after you finish the shift and get back on the throttle?

Knut
 

·
Registered
Joined
·
2,309 Posts
BOV protects the intercooler, engine and the turbo. If you are on full boost and suddenly close the throttle, as in the light changing on you, approaching a corner at the track etc., the air suddenly has nowhere to go. The turbo has inertia and is stillturning at full speed. The throttle is closed and the pressurized air is trapped. If the BOV does not open and release all that air,m the follwing will happen:

1. There is a pressure spike and, it may burst the intercooler. The intercooler is usually the weakest link.
2. The same pressure spike may get to the engine and cause detonation or the car will actually feel like it speeds up when you apply the brakes.
3. The air may surge and so bad things to the engine. This is not likely with modern engines.
4. The air will try to reverse through the turbo and back out again. This can do much damage. It puts a lot of stress on compressor blades and may rip them off. It puts a lot of stress on turbo bearings. It causes turbo surge that does more of the same.
5. The turbo will suddenly decelerate to the appropriate speed, so when you hit the gas again, as after apexing a corner at the track, you will have excessive turbo lag.

So, a BOV is a very simple and useful fevice.

It is just a valve on a diaphragm with one side connected after the throttle and theother before. The pressure differential across the throttle (which only happens when it is significantly closed) opens the BOV, and bleeds off boost.

If your case has a MAF, BOV to atmosphere will cause a rich condition, since the MAF thinks all that air went into the engine. REcirculating BOV's put the air back in front of the turbo but behind the MAF. This has an added benefit of keeping the turbo spooled up, but the plumbing is more complex. Also, the satisfying BOV sound cannot be heard!

Anton
There are two set ups.
1) Throttle-plate is between you blower and the engine.
2) Throttle plate in front of the blower.

In the first case there is no pressure spike that gets to the engine unless the throttle plate is hosed.

For the later case there is no pressure spike.
 
1 - 18 of 18 Posts
Top