Boost - is 14psi too high?

[frozen]

I did have a quick search, and i still couldnt find a perfect answer... Boost - mine is ~14psi with a MBC, and i had a friend say i would blow something up.... true or false? Just after an answer in black n white lol... Read here and there 12 from some, anything under boost cut from others whats the answer..? am i fine on 14psi? i have seen it spike to about 1bar, and hit fuel cut just over 1bar once, but turned it down a bit since then..

 

[Sydo]

It will be fine. The ECU programmed boost cut will save you from any dangerous spiking.

 

[bradc]

14 psi is fine

 

[frozen]

good to know - just had to double check... also is it going to be obvious when/if the car knocks? first performance car here...

 

[naughtika]

i'd say set it to 10psi.. with 14psi you might get boost cut more often.. which I experienced..

 

[bradc]

It depends on the mods done to each car though, some people can run 15psi and never have a problem.If the ecu detects knock above a particular level, it will cut timing. You're best to just use 98 octane and trust the ecu to sort out anything else.

 

[frozen]

i'd say set it to 10psi.. with 14psi you might get boost cut more often.. which I experienced..

I only hit boost cut once, that was at about 15psi, and on a very cold morning while the car was not completely warmed up yet turned it down a click or 2 and never had the problem again.

Mods are the exhaust, and the boost controller oh and cant forget my super cool "stock" intake pipe LOL

 

[Guest]

Detonation is not very obvious , especially for a novice. But the factory boost cut is normally sufficient to protect its limits. 14 should be fine.

 

[jungle]

Detonation is not very obvious , especially for a novice. But the factory boost cut is normally sufficient to protect its limits. 14 should be fine.

Guys,

Boost cut and detonation in this instance have nothing to do with each other.

You don't get the boost cut because the car is detonating, or even close to it- the boost cut occurs because the ECU is programmed for a certain amount of air in its normal tune. Once that goes above the pre-set amount (because you've turned the boost up), the ECU cuts ignition and Oila- boost cut.
Its a protection factor based on airflow- nothing else.

IF and that's a big IF, the ECU detects detonation, it will retard the timing. But you have to understand the factory tunes are very conservative and the only way i see you getting anywhere near detonation in this engine is running too low an octane.

Detonation is another story. It's the spontaneous combustion of fuel air mix, prior to normal combustion taking place.
Normal combustion burns around 30ft/sec detonation burns ~1000ft/sec

Now detonation occurs from a number of things
1. too low an octane fuel.
2. too lean a mixture (definately not the case in the Legnum)
3. too much ignition advance
4. too high cylinder head temp
5. too high an inlet charge

There are a few others, but these are the main ones.

Hope that clears a few things up

 

[frozen]

i run 12 now anyway, and make 188.9 at the wheels i don't think i need 14 for now till i got a bigger cooler, piping and dump + front pipes, then im going to aim for 220 somehow...

 

[jungle]

i run 12 now anyway, and make 188.9 at the wheels i don't think i need 14 for now till i got a bigger cooler, piping and dump + front pipes, then im going to aim for 220 somehow...

So you've got a cat-back exhaust and bog standard everything else, you're only running 12 psi punching almost 190awkW????

You must have a freak of a car Josh- would you mind posting me or redirecting me to your dyno graphs as i'd love to see them. Or at least tell me the name of the dyno place?

 

[Guest]

Maybe he meant 188.9hp? Not kw?

 

[naughtika]

its 188.9kw at all 4.. saw it myself

if it was in hp.. he'd be sh!tting himself.. lol

but yah I'm glad his car put out that much..

 

[scientist]

the boost cut on a cold day is kinda common.

Remember these cars use a MAF which basically detect airflow, not boost. So if it sees airflow above its limit it will induce boost cut. Since the maf helps compensate for temperatures, it cuts it even easier in cold weather because of the denser air.

 

[Guest]

What do you mean by if it was hp he'd be shitting himself? kW are more powerful than horsepower?

 

[SiliconAngel]

Because the car would be severly underpowered and he'd think there was something major wrong with the car...

 

[frozen]

So you've got a cat-back exhaust and bog standard everything else, you're only running 12 psi punching almost 190awkW????

You must have a freak of a car Josh- would you mind posting me or redirecting me to your dyno graphs as i'd love to see them. Or at least tell me the name of the dyno place?

It was 164 before the safc was tuned, they leaned it as much as they could without pinging or something.. 188.9 at the wheels after tuning. Some rev ranges are even minus 16 percent. Took them 2 hours of tuning. Apc on logan road. The car has a few things, check my thread in members rides for the dyno sheet.

edit - I re-read it on the computer rather than on my phone. my car isnt bog standard came with quite a few 'track' extras, and every few weeks i come across something new... aftermarket radiator, the other week it was the front rotors and the oil cooler/filter relocation, a few weeks before that was the ralliart braces under the car to match the suspension... but yeah performance wise the main things (that i know of) are the boost controller and cat back.

 

[naughtika]

What do you mean by if it was hp he'd be shitting himself? kW are more powerful than horsepower?

I meant if it was 188hp.. then he'd be sh!tty cause its not putting out that much power.. and he'd already spent alot of $$$ on it..

 

[jungle]

Have you got any dyno graphs?

 

[frozen]

just that one which shows tractive effort and the resultant kw. (afaik the kw is based on tractive effort in N into some calculation with the rpm?) Anyway, im yet to chase them up about getting some other graphs if they have them saved...