As above, whats the purpose of having a high and low boost map?

I see threads where people have even 5 different boost maps all switchable. Is it just a gimmick to impress people down the pub?

 

It's to give the option of different power levels. I had switchable maps on my 400+bhp BMW, found it very handy to adjust power to suit the conditions and situation.

 

If youve got a high boosting 2wd cossie I would think a lower boost map would be very helpful in wet.

 

That's what a accelerator peddle is for

Mark

 

I do it in most cars I map and most don't use it

Mark

 

Why not control the desired boost with the accelerator pedal in these situtations?

 

Interesting. Why do you do it though?

 

i don't think I ever switched mine into low apart from when you mapped it

 

The boost came in very aggressively with a huge torque spike, hence full boost actually hindered the car's progress at times. Feathering the throttle pedal doesn't do an awful lot in that situation accept make it hairy to drive, which is great fun, but again, not what you want at times.

 

Most boost control setups used on cossies don't allow for boost control with the throttle

 

You know what i,m getting at Mark. good throttle control combined with a softer less aggresive map for wet conditions would be useful.

 

Please explain further?

I am not talking about mapping boost to the trottle position or gear.

If you have a 20psi map and 10psi map surely the car will produce 10psi at the same rpm?

 

Because they pay me

Mark

 

Ah I see, I thought by your post you were implying it is something you do with every mapping as standard.

 

Mark put high and low boost, plus launch plus anti lag, this means I now have 3 nice switches that will never be used apart from the time that I tested them to see that they work. If I take my car to prescot hill climb I expect I will use the pop / bang on the line as everyone does to show they have it and that is it....if it is in the ECU and the loom provides those wires then you may as well make them work? I guess I might put it in low boost if a friend drives it but 400 bhp and 468 bhp is probably just as much of a handful? I like the idea of a hidden "no boost" switch so that the MOT tester can move the car about without the temptation to rag it but I know the local testers and would egg them on to try it out on full boost.

 

Are you talking about swapping between a high and low boost target map or actually swapping between two fuel/ign maps?

I often use more than one map to increase resolution in areas like idle and cruise. For example, I might swap maps at 10psi from one 16x16 table to another 16x16 table which means one table has 256 cells devoted purely to power runs and another has 256 cells used mostly for cruise and low load stuff. I also do the same with ignition maps for idle if a car has a silly cam.

We also use multiple maps for things like track/road. The only difference here is that lean cruise is ignored and idle is a little richer as well as high load to keep temps down a little.

Or if your talking about why have multiple boost target maps???? Well I guess you trust your missus to drive your car as is ..... other than that I don't think it would ever be touched.

 

Ive never had mine in low boost & cant remember Mark mapping as such he knows its a redundant switch in mine. Why have 650 when you can have 850. You lose torque with the low boost & that's not something I want .

 

More or less, the 20psi target would probably mean you made 10psi a little sooner as the waste gate would be fully closed. If you target is 10psi the waste gate will begin to open before 10psi to avoid overshoot.

 

Common on WRC cars now. They have road and stage modes so they can save fuel on road sections and can also have different maps for different weather conditions.

 

I am talking about multiple boost target maps. I assume thats how most fast road cossies and rs turbos are mappped when they have a high/low boost?

I see. So if all you have is a switchable boost target map it essentialy does the samething you could be doing with the accelerator?

I am just trying to understand the real world benefits of say a 10psi and 20psi boost target map.

People say for traction in the wet etc, but could you just not press the accelerator any further once you reach 10psi on the 20psi map? The 10psi map would just mean you can hold 10psi at 100% throttle to the limiter instead of 20psi. But why would you be driving that hard to hold 10psi to the limiter in wet conditions?

Any help is appreciated. Trying to understand as much as I can.

 

For me it must be a pretty crap ecu if you have to do that to get nice fuelling.

Mark

 

Some people have no feel for it but also the way I see it is you don't drive as hard in the wet on a public road.
On a race track you would be better off reducing the power to suit the road so max accel can be used.

Mark

 

You can't do it accurately and efficiently with a cable throttle car with just your foot in every gear.

You try and run 1 bar boost through the RPM range on your 2 bar capable car. You can only reduce boost by throttling the engine, but the throttled point of operation is constantly changing with RPM. Also a throttled engine is inefficient, you want the throttle as open as possible, along with the wastegate, for as long as possible.

Rick

 

See switchable maps on subarus all the time for methanol ect

I don't see the point on low boost as you can just use less throttle and no boost will come in, I'd prefer high boost map I.e 2.0 bar and really high about 2.5 just for when someone is beating me lol

 

You mean you wouldn't want 2 different boost settings...let alone 12!?

 

Driving around you get used to it and feel the need to join the slippery slope to going faster.

Drive around on low and then switch to high every now and again to remind you it's plenty quick enough and leave the hell alone.

 

I had it on my 3dr - was very useful especially in the wet but then again as soon as that car saw boost in the wet it was all over the place anyway.

It came in handy when i let other people drive my car so had it set on lo boost

 

Same here, only used the low boost setting when Mark mapped the car

 

Not really Mark I do the same with different ecu. People use various maps compensators or scalers to the same effect even with incredibly high end units.

Oem ecu's also do the same and have many multiples of maps spanning different target operations. Cruise, Idle, lean cruise, map per gear, maps for various throttle angles, granted a lot of that may be emissions related.

In some respects I find it nicer to map like this as each map has a specific purpose and separates the end goal into chunks, one map which I tune on the dyno and another which is largely tuned on the road etc. a side benefit is an increase in resolution. I find it works exceptionally well but understand that every one will have a different approach to solving the same problem. It maybe that the extra resolution gained is not needed but I've never turned down a free sandwich yet.

 

Cal switch is commonly used for all sorts, different boost levels vs fuel type to name one, we use a 12 position switch for 3 setups depending on fuel, restrictor size and boost level , all fine and well running the engine flat out all the time but it's added wear on the engine and transmission.

A simple high/low boost switch is effective enough on wet track days in a 2wd car

 

what does that mean then? Keeping the temps down?

 

If you have a richer map the engine runs cooler same as if you lean the map out it gets warmer.
Fueling is a bit like heat managment

 

but more fuel means it's got more to burn, and if it doesn't burn it, it just goes out the exhaust or down the bores doesn't it?

or am i getting the wrong end of the injector here?

 

Sounds like some make things far more complicated than it needs to be lol get it mapped drive it if it's wet don't drive hard

 

Its exactly that, a richer mixture either doesn't burn and/or has a slower flame front which leads to lower combustion temps and in turn to a lower egt.

 

Most old school switchable boost systems just fall back to waste gate spring pressure. Which is normally 7psi for the majority of rs turbos with standard actuators.

In the wet less torque may mean higher acceleration as the acceleration will be determined by traction. Most normal people would just lift off the throttle.... I genuinely only ever use a switchable boost map when someone else is driving the car ie, my mrs.

My old (and never driven ) Rs turbo switches between 7psi, 18psi and 24psi. I always drive it on the 18psi map as it drives well at 18psi and is kind of tractable. It was mapped at 24psi but is a torque steering mess at 24psi and useless with anything other than good tyres and sunshine. 7psi is just there in case I can't drive it home for what ever reason, the car starts up on the 7psi setting and the switch to change is hidden under the dash.

 

Kids today hey everything has to have more buttons than a playstation

 

if you have it fucking use it.

 

you have nipples - do you use them?

 

Thats funny.

But I guess if they did something maybe he could