I know this maybe a tall order,has anyone have any printouts of their cosworths running siemens 55/t34.48/ 7.5-1 cr running around 330bhp.
I'm gonna be taking my car to msd for a full setup in a few weeks,looking at a dyno printout i had done the power starts to tail off a 5500 rpm,proving what i can feel when driving(i thought it was running to rich).I want to do as much as i can to the engine to try and correct it before i embark on the 800 mile round trip. Just want a quick comparison,to either see if its way off normal or just slightly out.

very much appreciated
Matt

 

i would think on a 0.48 turbine housing its just getting to restrictive at 5500 rpm, that's why i got rid of my t3 on one of my old saphs as the top end was rubbish.

 

Thats what i'm kinda hoping it is,i'm thinking about the ££££££££ it may cost to put it right otherwise
thanks scooby

 

i would also say the ex housing is the restricting factor in this, could always upgrade to a .63 for more pull top end

 

 

seems a good set up and very impressive torque figure

 

Any thoughts on changing inlet cam,been chatting to few,and seem to think i could get longer top end,would i lose it low down.
cheers
Matt

 

If you don't have valve cutouts use a AB07 inlet cam, it held onto the power so much better in mine and lost no noticeable bottom end pull

Steve

 

hmmm,i have valve cutouts

 

The limiting factor in your spec is undoubtedly that turbine housing and potentially also your boost control. The .48AR turbine housing is tiny and restricts the engine massively from 5000rpm upwards. If you want more top end power, fit the .63 to extend the powerband upwards, but for the best power you really need some form of programmable boost control, ideally air injectors as that gives us good rpm control too so we can push the turbine at high speeds.

Ultimately though, its all down to how you want to drive the vehicle. Do you want big slugs of low end torque so you can shift at pretty low rpm or do you want to push her to the rev limiter every change and need a more linear power delivery due to the minimal weight of the vehicle?

 

Thanks for the info stu,I like the punch in gives,but at least i know its normal to run out of steam when it does,I may try a bigger housing, as its a pretty simple change if i don't like it.Are air injectors a simple plug in,(just for a bit more control?)then you alter the map to suit.i'm assuming for complete control i would have to use an aftermarket controller(Don't want to go down this route,as its a bit much for the odd track day,and a sunday blast).
Oh,do you have to alter the chip for a .63 housing
thanks again stu
Matt

 

Hi Matt,

The Air injectors require a chip change and mapping in as they are mapped on load Vs RPM which means I can program what your boost does at any RPM. IE: peak at 38 between 4 and 5krpm and hold 30 from 5k onwards for example. Top end boost is very turbo dependant as it can only flow what it can flow and the YB will always ultimately consume more air than a T34 can give at 30psi, but Air Injectors will ensure we can get the best from it.

Aftermarket are exceptional at holding boost as they Are closed loop feedback controllers, however, unless you have one with built in RPM control the inbuilt overboost facilities can be quite dangerous on an engine pushing injector on time hard as a 38psi spike at 6.5k for example would kill a YB on 55lb Siemens, so the rpm control is of paramount importance. The alternative is to just hold a solid figure with no spike at all and this gives a nice linear power delivery and for this, jap controllers are awesome.

Here's one I tuned exactly that way this week.