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How Much Bosst

robwright

robwright

New member
Evening all. You may be aware from recent posts I am now all set up with my DPW boost gauge and AFR. I am currently making good boost of 15 psi and boy is the car quick. In fact it's bloody quick. I know there is more to be had though as even without using the AFR I know I am still running a little rich when I bury my foot in the carpet. My question is what is a pretty sensible (OK not so sensible) boost level to aim for without going too bonkers. Also what is a good AFR reading to aim for to accompany it. The use of the AFR is all pretty new to me. Although I have to admit it did show up a minor exhaust leak that I had. Quite impressed.
 
LOL very tempting Peter but she also is my daily driver. And very proud of her I am too. Any more suggestions mate?
 
Sorry Rob, can't really offer a sensible answer (especially after a bottle of cheap plonk) but I'm sure someone will be along with an idea of where the limit is likely to be.
 
Only go to the boost setting your chips are mapped for - the DME/KLR does not fuel according to boost - boost pressure doesn't even figure in the fuel and ignition maps. Go above at your own peril. Aftermarket chips are usually conservative (at least the ones that don't break engines are) so will intentionally run you rich to keep combustion temps down. Increasing boost over and above what you are mapped for is a dangerous game even if you maintain AFR's and will undoubtedly end in tears. AFR's is only one half of the story, there is also ignition timing which is sensitive to boost, so if your ignition is mapped for 1 bar and you run higher boost then you'll be too advanced and risking your engine. If you want to vary boost you need to go to a proper MAF kit (not an AFR to MAF conversion kit) or go stand alone or at the very least get a custom map at a specific increased boost level. My advice is be satisfied with what you've got for the moment and if you want more install the proper kit before increasing boost.

In anycase, it is often accepted that 1 bar boost with a 3 bar FPR is about as much as the stock injectors can cope with, though some run upto 1.2bar boost, but you don't want to be running 20yr old injectors at 100% duty, or anywhere near 100%.
 
I'd argue that it should not be a consideration. Head gaskets break due to temperature, i.e. poor tuning, and not boost pressure. As long as good tuning is maintained throughout and combustion temps are kept in check then the head gasket should survive unless it is already on it's last legs. However, that's the theory, in practice it might be prudent to replace the HG.
 
Scott I see your point mate and on reflection I think I am inclined to agree. (at least for now anyway). For the near future anyway the car will continue to be my daily runner without a back up. I suppose 1 bar is not to be sniffed at really and it is quite easy to get caught up in the quest for boost lol!!! I certainly upset a Nissan 350Z driver last night when he couldn't undertsand why the 21 year old car gave him a good run for his money and still had some left in reserve!!! The car has consumed a lot of my sheckles over the last month and there is no more in the piggy bank at the mo. I have just found out there is a dyno round the corner from me £65 an hour which I think is quite reasonable. Might just squeeze to an hour to see where I stand at the mo and they do custom maps for an afternoon session. Perhaps something to think about next year. Time to concentrate on the little stuff thats been neglected I think like the sunroof etc. Yeah you all know the little jobs lol. Thanks for your advice mate.
 
Powertec Engineering.
24 Ivatt Way
Pboro

Appparently there is another in Werrington as well. Will try and get the details for that too.
 
ORIGINAL: sawood12

I'd argue that it should not be a consideration. Head gaskets break due to temperature, i.e. poor tuning, and not boost pressure. As long as good tuning is maintained throughout and combustion temps are kept in check then the head gasket should survive unless it is already on it's last legs. ........
Click to expand...

Indeed. I run 1.2 bar boost (17.4 psi boost) with a standard head gasket but am running quite rich on boost.
 
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