The '2 ton bugswatter' - back for a gentle stroke

[Bram]

Nice top-end power, but why is the boost profile so high up the revves? what cams are you running?

Stunning engine bay btw! I like it

[JP]

^^^ I'm running an experimental 7A profile that I wanted to try out. As on paper it looked like an interesting configuration to achieve the end target for my trackday outings whilst providing a very smooth power delivery when used as the family car. I still got a bit of tweaking to do on the vernier side of things, just haven't had time to pull the front end of and install them yet.

As for the engine bay it's a bit dirtier now the weather hasn't been that kind to it

[A80Avant]

thats a shame that this happened.

i too got a similar ring to stop the turbo from whistling.It works nice!

didnt have to go through the MAF issues as im in vems mode!
As i mentioned before, for some reason motronic does not seem to like tuning boost for those garretts. As soon as i went to vems, boost control was made easy!

[A80Avant]

I would also dare to doubt that a restraining filter could cause damage to the turbo, esp considering all the applications these turbos have.

[JP]

I would also dare to doubt that a restraining filter could cause damage to the turbo, esp considering all the applications these turbos have.

I'm also in two minds about the explanation. The theory is if the turbo is trying to suck in more air than the filter can supply it puts negative pressure on the seal instead of positive pressure which it requires to seal properly. Pretty much the same as your piston rings.

It's either that or I was sold a faulty turbo, as it has been functioning perfectly fine for over 5000miles since the rebuild running much higher boost pressures.

[A80Avant]

i was running 2.1bar and 1.7 steady on a 3071 turbo on stock air filter box(rs2) with panel KN filter. Never had an issue. There is logic to what they say, but i cannot believe the turbos are so fragile... i dont know..

[JP]

^^^ just out of interest ported/stock head? Modified or stock cams? Reason I ask when one measures boost they are measuring what is left over in the intake. i.e. what the engine cannot use/swallow.

This is best visualised with a supercharger which does not have boost targets but instead linear delivery being belt driven. If you have say a G60 engine running 19psi of boost on a stock head, replace the stock head with a ported head and this will drop to 11psi, now go big valve and match the intake manifold and it can drop down to 8-9psi.

Charger still delivering the same amount of air as before just the engine is using more. So if you now try and make the charger spin harder by running smaller pulleys you are going to start finding limits where either the charger can't provide enough airflow or it can't take enough in through the filter.

So when you have a turbo car that is not very efficient it can make boost very quickly and easily go into surge as the compressor housing is providing more airflow than the engine can cope with. In the same token make the engine more efficient and although you come on boost later you will be producing more power at the same given rpm as the other less efficient engine providing the turbo can swallow sufficient air for it's requirement.

[GazzaG60]

thats the ticket.

the thing with the sc over the turbo is you see the changes. you see the efficiency in engine gains by boost dropping. on a turbo the gate pressure will mean the turbo just flows more. its essential you know what the turbo can do or it may be becoming a fireball.

on the G60 the cam is the biggest issue. thats about a 4psi drop, 15-20hp gain. i ran a 65mm on mine. it made 19psi. thats about it on a glader.

alsoits important to think about how the air is compressed. air is stacked on a turbo on a G60 its a eccentric compression method.

a turbo can suck harder thana G60 and ive seen G60's turbo poor flowing filters inside out almost.

filters need surface area. 2 filters the same size. pick the one with the most folds.

[martinjs]

Any updates JP? Do you have any pics of your FMIC? What size is it?

[JP]

Sort of been really busy and sidetracked because of trying to juggle kids with work, but I've just pulled some pics of the camera.

Intercooler is a £60 job from ebay.





It required hacking out the back of the bumper to fit whilst retaining the aircon





The spec of the intercooler is a 300x450x75 ccore bar and plate with 63mm in and out.

Boost run consists of SFS hoses and their billet couplers for simplicity and is as follows

straight hose of turbo to 60mm dia with DV take of, billet coupler, 90 degree 60mm, billet coupler, 135 degree 60mm, intercooler, 45 degree 60mm, billet coupler, 90 degree 60mm.

This then brings it exactly to where the original sidemount intercooler exit was. From where I then fitted my MAF relocation contraption from earlier in the thread.

That particular setup produced the 528hp and 427ft/lb the engine saw on a ported .63 backhousing on the 30R hybrid. as shown below



The line with more power and torque across the range is from after I fitted the verniers and dialed the cams in to suit. The dip is from an ignition pull due to fuel pump voltage drop which has been sorted out since by wiring direct to the battery via a relay. We haven't been back on the dyno since purely down to time.

Instead I thought I try a bit more experimentation and have temporarily fitted a stock head alongside a ported .82 backhousing. You can see how much bigger it looks on the right.



Initial views are, laggy nothing nothing nothing and then sort of bang. I struggle to make any sort of boost over 1.9Bar and the car feels flat. I'll be putting it on the dyno either later this month or beginning of next to get a baseline figure before putting the ported head back on and seeing what the difference is to a stock head after which I can also compare the .63 to .82 housing on paper. In real life it is definitely less vicious but the .82 does pull nicer at the top with lower EGT's with so far no real difference on the quarter.

Once I got those figures I'll get my behind into gear and decide what combo stroker engine I'm going to opt for, as to whether I'm going silly power or keep the threshold not much higher as it is and leave it sensible as a daily hack.

I've also still got a set of Cayenne calipers I need to get round to fitting which I may decide to do before fitting the stroker as the brakes are starting to get mildly entertaining during track days

[JP]

OK teensy weensie update, popped past MRC the other day to chuck the car on the dyno for comparison purposes.

We got two dyno plots

1 - ported head (stock size valves) with a .63 backhousing

2 - completely stock head (refurbed) with a .82 housing

I'll let the graph do the talking



I'm just in the middle of reworking the head with .5mm oversize valves and a new combustion chamber design after which I'll do a 3rd pull with ported head and .82 backhousing for direct comparison with the larger hotside at the same boost level as the stock head (can't get any more boost form the stock head). Then a 4th pull where we'll up the boost pressure to around 32psi where I was running the .63 housing at. Probably gonna start pulling a couple of late ones to rush it along as missing the more pokey feel

[Bram]

Wow, that is an enourmous increase in top-end power. I was not aware a 0.63AR GT30 could go above the 500HP mark.

[A80Avant]

so according to the graphs, the 0.82AR gave you faster spool??

cause No1 on the graph only goes to 449hp and the No2 goes to 529hp. although the torque is still later than the No1, is much higher

[Billman]

I think green is 0.63 with head done!

[JP]

^^^^^ Yep green one is ported head with .63 housing, spools sooner and produces more torque and hp across the range than the stock head with .82 housing which is the black lines.

Have to say never been so happy to see such a big loss on a dyno by temporarily going back to a stock head