Rev cold racing-engine

[Christoffer]

A couple of years ago I read in Evo magazine a letter posted by a reader.

It went along the lines of: I've heard that some touringcars or sportscars are being revved imediately following start up from cold, and then turned off again.

Evo answered something along the lines of: The teams rev the engine to get the oil splashed around everywhere so all the internals and valves etc. are covered in oil. That should then be good for a later start up.

Alright I really don't understand why they would rev the engine from cold, that must surely put a lot of stress on the entire engine right?

And why turn it off after revving it? It's still cold if it's just been running for 15 seconds. Will that short a running period in any way have a noticeable positive effect of the engine and oil temperature?


Can anyone please enlighten me on these two question? I am a bit confused as to why you'd rev a cold engine...

Thanks

[HRG]

The article was utter garbage, that's why you're confused Revving a cold engine is the best way to wear it out

[agent006]

I would imagine they use an external pre-heater to get the engine warm before starting anyway.

[Christoffer]

HRG said:

The article was utter garbage, that's why you're confused Revving a cold engine is the best way to wear it out

Thank you!

That's what I thought

[Christoffer]

agent006 said:

I would imagine they use an external pre-heater to get the engine warm before starting anyway.

Would they use that on a touringcar engine?

I believe they are 2 litre and develops 280BHP which isn't that heavily tuned really. Thus, they might not need to pre-heat it?

[Mikey G]

Christoffer said:

agent006 said:

I would imagine they use an external pre-heater to get the engine warm before starting anyway.

Would they use that on a touringcar engine?

I believe they are 2 litre and develops 280BHP which isn't that heavily tuned really. Thus, they might not need to pre-heat it?

280bhp in a N/A 2 litre isnt exactly a mild tune though!

[Christoffer]

Mikey G said:

Christoffer said:

agent006 said:

I would imagine they use an external pre-heater to get the engine warm before starting anyway.

Would they use that on a touringcar engine?

I believe they are 2 litre and develops 280BHP which isn't that heavily tuned really. Thus, they might not need to pre-heat it?

280bhp in a N/A 2 litre isnt exactly a mild tune though!

For a racing car engine I would say it actually is quite a mild stage of tune. The internals are very different from high-output road car engines and I would hazard a guess the engines run for a relatively low number of hours before they are inspected.

Granted, 140BHP/litre in a N/A road car engine is a very high state of tune.

[Pumaracing]

Christoffer said:

agent006 said:

I would imagine they use an external pre-heater to get the engine warm before starting anyway.

Would they use that on a touringcar engine?

I believe they are 2 litre and develops 280BHP which isn't that heavily tuned really. Thus, they might not need to pre-heat it?

Not that heavily tuned??? It's as highly tuned as they can get a modified small bore long stroke road based engine unless you think you're some kind of tuning god who could do better. It's not a very high specific power output compared to an F1 engine where the bore stroke ratio is much higher and more valve area can be employed but you work with what you're given and what the rules allow.

[agent006]

Pumaracing said:

Not that heavily tuned??? It's as highly tuned as they can get a modified small bore long stroke road based engine unless you think you're some kind of tuning god who could do better.

No, it's as highly tuned as BTCC regulations will allow. Given that 20 years ago BMW were pushing 350+ out of a 2.3 in the M3, i'd say 280 is rather conservative as race engines go.

[Christoffer]

Pumaracing said:

Christoffer said:

agent006 said:

I would imagine they use an external pre-heater to get the engine warm before starting anyway.

Would they use that on a touringcar engine?

I believe they are 2 litre and develops 280BHP which isn't that heavily tuned really. Thus, they might not need to pre-heat it?

Not that heavily tuned??? It's as highly tuned as they can get a modified small bore long stroke road based engine unless you think you're some kind of tuning god who could do better. It's not a very high specific power output compared to an F1 engine where the bore stroke ratio is much higher and more valve area can be employed but you work with what you're given and what the rules allow.

Does that have to do with the burn rate of petrol and the distance the piston has to travel in that kind of engine?

I'd imagine there are other kind of restrictors (air) or otherwise in the regulations that make it difficult for the teams to go over this BHP.

Well my original question had nothing to do with how fast petrol burn but more to do with what I read in Evo magazine which I thought was very strange indeed.
A road motorcycle e.g. can have a N/A power output of close to 200BHP/litre and they don't need to be preheated or "revved" from cold and what not.

So no I don't think the engine itself is very higly tuned and therefore not that stressed. That petrol might not burn fast enough for that type of engine to be able to rev higher and create more max BHP wouldn't really mean that much to the rest of the internals. I am 100% certain they can easily get more power out of a 2 litre engine if the regulations are different.
A Lancer evo FQ400 or what it's called, produces 400BHP from a 2 litre but it's turbocharged. Many of that engines internals must be more stressed than in a 280BHP N/A engine.

Great get some constructive feedback Pumaracing and looking forward to hear about why it's difficult to go over 140BHP/litre within the BTCC regulations.

[Munter]

I terms of power that can be generated you'll start to get into a physics conversation.

To make a fire you need air and fuel and ignition. The last one is taken care of with the spark plug(s).

If you concentrate on air and fuel then the main problem is getting enough air in. Given petrol is now injected under high pressure we can get plenty of that in there. Although there are issues around getting it to "mix" as you'd want.

Back to Air you only have air pressure to push the air into the cylinder. The smaller the "hole" in something the less air you can get through it at a constant pressure difference(atmosphere vs "residual cylinder pressure"). So you need to make the hole bigger. So bigger valves on different timing. But you are limited by the basic design of the engine as to how big the valves can be and what timeing can be used. Massively oversquare engines allow you to have bigger valves = more power.

Thats Phils very simple understanding. However Dave knows this stuff much much better.

[Pumaracing]

Christoffer said:

Does that have to do with the burn rate of petrol and the distance the piston has to travel in that kind of engine?

No. Not even remotely. You need to read the articles on my website rather than me starting a tutorial on engine theory from scratch for one person.

http://www.pumaracing.co.uk/

The ones on Power and Torque and the ones on Evaluating an Engine's Power Potential a bit further down.

[Christoffer]

Pumaracing said:

Christoffer said:

Does that have to do with the burn rate of petrol and the distance the piston has to travel in that kind of engine?

No. Not even remotely. You need to read the articles on my website rather than me starting a tutorial on engine theory from scratch for one person.

http://www.pumaracing.co.uk/

The ones on Power and Torque and the ones on Evaluating an Engine's Power Potential a bit further down.

Hi Pumaracing,

Thank you very much for the link. I look forward to reading the article!

[Icarus_]

Christoffer said:

A couple of years ago I read in Evo magazine a letter posted by a reader.

It went along the lines of: I've heard that some touringcars or sportscars are being revved imediately following start up from cold, and then turned off again.

Evo answered something along the lines of: The teams rev the engine to get the oil splashed around everywhere so all the internals and valves etc. are covered in oil. That should then be good for a later start up.

Alright I really don't understand why they would rev the engine from cold, that must surely put a lot of stress on the entire engine right?

And why turn it off after revving it? It's still cold if it's just been running for 15 seconds. Will that short a running period in any way have a noticeable positive effect of the engine and oil temperature?


Can anyone please enlighten me on these two question? I am a bit confused as to why you'd rev a cold engine...

Thanks

Ignore that article, as previously stated its bks.

Nearly all BTCC, WTCC, Sports Saloons etc. making the kind of power figures common in BTCC (i.e. 130bhp/litre naturaly aspirated +) use pre heaters before the engine is ever started.

These are usualy an external coolant pump and heater element which pumps the engines coolant through the engine, rad, oil cooler (if water/oil) etc. and brings the engine temperature upto 80 - 90 degrees.

The short run time you see occasionaly is usualy for an electronics systems check. The engine is fired and run for a short period of time at a range of RPM's during which all data is logged (at circa 1000 samples/sec +) and then reviewed post engine run. This allows teams to identify any issues, sensor calibration problems etc. etc. with time to spare and without the car being on circuit.

Once complete the car will be put back on pre-heat (if required) until it is ready to race in order to avoid a complete engine package heat cycle.

Cheers
M

[Christoffer]

Icarus_ said:

Christoffer said:

A couple of years ago I read in Evo magazine a letter posted by a reader.

It went along the lines of: I've heard that some touringcars or sportscars are being revved imediately following start up from cold, and then turned off again.

Evo answered something along the lines of: The teams rev the engine to get the oil splashed around everywhere so all the internals and valves etc. are covered in oil. That should then be good for a later start up.

Alright I really don't understand why they would rev the engine from cold, that must surely put a lot of stress on the entire engine right?

And why turn it off after revving it? It's still cold if it's just been running for 15 seconds. Will that short a running period in any way have a noticeable positive effect of the engine and oil temperature?


Can anyone please enlighten me on these two question? I am a bit confused as to why you'd rev a cold engine...

Thanks

Ignore that article, as previously stated its bks.

Nearly all BTCC, WTCC, Sports Saloons etc. making the kind of power figures common in BTCC (i.e. 130bhp/litre naturaly aspirated +) use pre heaters before the engine is ever started.

These are usualy an external coolant pump and heater element which pumps the engines coolant through the engine, rad, oil cooler (if water/oil) etc. and brings the engine temperature upto 80 - 90 degrees.

The short run time you see occasionaly is usualy for an electronics systems check. The engine is fired and run for a short period of time at a range of RPM's during which all data is logged (at circa 1000 samples/sec +) and then reviewed post engine run. This allows teams to identify any issues, sensor calibration problems etc. etc. with time to spare and without the car being on circuit.

Once complete the car will be put back on pre-heat (if required) until it is ready to race in order to avoid a complete engine package heat cycle.

Cheers
M

Icarus_

Only read your answer today.

Thank you very much for your reply which I appreciate!

Could you tell me, why would you not want a heat cycle? Does a heat cycle put any strain on the engine that could in any way be detriment to the longevity of it?

I have heard that oil ( engine, gearbox ) will deteriorate when it's going through a heat cycle but didn't know that the metal would deteriorate. If I understood your last sentence correctly that is.

Cheers mate

Christoffer