My TD05 FE surges from about 3300-3800 RPM in 4th or 5th gear running 1.5 bar in this area. It is fine in 3rd gear because the boost comes in a bit later.

If I let it spool up to 1.25 bar at 3000 RPM, and then amble up to 1.5 bar by 3600 RPM it is surge free.

Do you think fitting a bigger exhaust would increase the volumetric efficiency of the engine in this area enough to let the engine flow better or do you think this would make the turbine wheel even friskier?

If the turbine wheel was cut back this should reduce back pressure and slow the spool up enough?

Interestingly in third gear with the slower rate of boost rise it still reaches virtually peak torque at 3500 RPM, presumably I am hitting more efficient areas of the compressor map, a less is more scenario. Is the exhaust side of the TD05 a little *too* frisky for its compressor wheel?

Just not had to deal with a surge prone turbo before, so any hints welcome. I am so used to going max attack on the duty cycle until full boost arrives which usually works well.

I suppose I could also reconsider headers which might increase flow and kill the spool up slightly.

David Wallis, did your TD05 surge when you were running 1.5 bar from 3300 to 3800 RPM?

 

Whats surge?

David

 

Take it it did not surge then? Maybe your exhaust is better?

 

HKS custom downpipe... HKS Hiper 3" exhaust..

I didnt feel any surge... pavlo might be better to answer..

David

 

John, I have the same issue with the Maxim headers if I don't slow the spool-rate slightly. At least, I assume it's surge - not as loud as I thought it would be, but you can hear/feel that the airflow isn't smooth as it comes online. Also only in 4th and 5th.

What I don't get is that the Evo guys convert the 05 to roller bearing....giving spool up at around 2k Why aren't these surging too? In the Evo, even stock, they spool up earlier than on the Scoob which is down to header length, I guess? So I'd have thought surge would be more of an issue....

Richard

Richard

 

350 ft lbs. by 3,500 rpms ??? oh how I wish

 

...get a tdi.

/J - sorry!

 

According to DD, I am in that ballpark at 3800 RPM in 3rd gear, maybe it will come a bit lower in 4th or 5th when the surge is sorted. However, on the rollers, the boost delivery is never the same as on the road, it will probably make its torque at 5000 RPM or something

 

John

I'm not sure that the 'fluttering' you are hearing is real 'surge' It is perhaps just getting close to the line ?
Real surge can sound like someone repeatedly hitting the floor of the car with a hammer as the power cuts in and out due to the backflow through the compressor

FWIW I ran my TD05 with this 'flutter' for most of last year and it suffered no ill effects. You can just go buy another one for £150 if it breaks anyway

Andy

 

just watch out that the compressor looses a blade (touches wood), and this goes through the air outlet

 

I hear you Andy, but the MAF voltage goes crazy when it happens and it is not very smoooth. I'll have another play tonight.

 

John, you have run it over to the wrong side of the surge line when that happens, if you calc it out you will find you do need to temper the spool to suit the turbo, fundementaly the turbo is stalling, not in speed but in air flow and the fluttering and maf jump is caused by air spillage back out of the turbo inlet which will then pulse at the maf. So too much boost and too little flow. Be careful as there are high shock loads on the compressor when that happens.

Lol Andy ...turbos are cheap its true, blade parts get everywhere though.

 

Isn't that why we fit FMIC's ? To filter out the lumps

 

andy when you say £150, is that for a second hand td05 turbo?

mike

 

second or even third hand

 

"Big capacitor" theory ...trouble is the air spill is before the turbo inlet not after the exit, intercooler does nothing for it.

 

I get the fluttering sound, but not MAF or boost variations...good

I tried clamping spool a little, but I'm back to living with the additional noise...it's not exactly a quiet turbo anyhow

I always recondition a 2nd hand 05 before fitting - full service kit (bearings/seals/gaskets) is remarkably cheap.

Richard

 

Lol Andy, I'll wake up soon ... been a hard week.

 

MY 98 304FTLB AT 3300RPM

 

All I get now is a slight audible fluttering, and a very slight flutter on the MAF signal to give about 308 lbft at 3500 and 369 lbft at 4500 running from 18 to 24 PSI in 3rd gear on Delta Dash. It does not lose out by holding the boost down from 3000-4000 RPM and makes it very easy to control the boost. When I had the boost coming in hard it was not pleasant to drive from 3000-4000 RPM.

 

cheers andy, thinking more for the near future, just sorting out my brakes and supension at the mo

mike

 

[Edited by QA Guy - 4/19/2003 5:41:52 AM]

 

<off topic>

Richard,

The EVO uses a twin scroll turbine and the engine with it´s long stroke is a lot more powerfull off boost compared to the Sub. That is why they have (a lot) more torque at low revs.

Mark.

<on topic>

 

I thought their off boost low down torque came from their 88mm stroke and 8.8:1 compression.

 

John - seeming that you commented on it in your initial post, I'm still not sure why you haven't changed your headers? They're always a little 'risky' to change, yes, but something like the HKS ones I don't think anyone has found any bad side-effects to (aside from them being a little pointless on tiddly-turbos) but I'm pretty convinced they would help in your case... must be worth a go, anyway? Heard good stuff about the 'ION' ones too, but no details

 

I had some headers before which worked well on the TD04 but not on a bigger turbo.

I reckon headers move your power band rather than fatten it, I am willing to be convinced otherwise though. There are plenty of other cheaper ways to move your power band. Gas velocity is king, and I also remain to be convinced of the effect of headers over an aftermarket uppipe. Some have suggested all but less than 5 BHP of the gains comes from the uppipe.

If I have trouble achieving my transmission friendly power/torque targets of 450/400 then I will reconsider headers.

 

The evo uses a much bigger ex housing. I think it's 9cm vs 7cm, but check with Dr Sam, he knows a lot better than I.

The surge comes from the compressor side, the sorts of increase IN VE you're looking at a minor when compared to the flow of air. I have seen a very nice map for a wheel that will allow much lower RPM at 1.5 bar on the TD06 cover, and we will see results of this shortly.

I think the exhaust side of things is really giving you more stable boost control.

My Legacy flutters all the time, even as standard, even at 1-2psi on light throttle, right up to flat out at 3500rpm and 15psi. The compressors do have a certain amount of slip anyway, so I think this will give you some odd sounds anyway.

Paul

 

Maybe Evo engines flow more at these engine speeds? Different cams, different engine configuration?

Can the Evo guys get more than 350 lbft before 3500 RPM out of a TD05?

I can see the surge on the boost gauge (+-1PSI flutter), hear it, feel it, and see it on the MAF sensor trace - it swings about 0.3-0.4V as it is surging.

[Edited by john banks - 2/6/2003 12:56:39 PM]

 

the blitz might help then?.

must remember to take the ear plugs as well as the body armour and hard hat when it's on the rollers .

[Edited by T-uk - 2/6/2003 1:34:18 PM]

 

oooow a cheap mod... unless andy buys them all
how much does it cost to convert them to straight entry?

sorry for hi-jacking the thread

mike

[Edited by FASTER MIKE!! - 2/6/2003 9:42:09 PM]