1996 855 T5 Sluggish boost build, Wastegate?

Angelofhevn · Post by **Angelofhevn** » 20 May 2019, 13:40

Hello. I have a 1996 855 T5 with these modifications
3" Turboback with 100cell cat.
New Td04h-18t Turbo with stock 15g wastegate. (stock wastegate hole was smaller than stock so i ported it to a little over stock 15g turbo size for controll)
Japan Exhaust manifod (2004 XC70)
Short ram intake with pod.
GLT Cams timed after IPDs specs.
New Pierburg Later v70 TCV.
New 960 MAF housing
Green Injectors
Motronic 4.4 ECU tuned by VastTuning Wideband regulated.
New AEM Wideband feeding ECU.
3" Airfilter to turbo feed hose
Custom PCV system
Stock 850 AUTO gearbox.
New Tcv lines

And the car is running great! But! The boost buildup is kinda sluggish. Sometime when driving say 20mph cruising and i step on it the car goes into wheelspin mode instantly and boost climbs quick and steady (1.1bar) . But then randomly (90% of the time) it accelerates like a turd with boost at around 0.6bar until 4k rpm and then it takes off with full power and boost! Kinda like VTEC on hondas. Like ketchup effect. I dont really know why. Im suspecting the Wastegate is getting sluggish and is too weak?

No effect with stock BCS or diy MAC valve. Pressure tested intercooler system and no leaks but intercooler bottom hole (stock). When i bought the 18t it came with a wastegate accuator but the barb to the TCV was wayyyy smaller than stock 15g barb. (inner hole 4mm stock vs 2mm 18t one) so wasnt comfortable to put it on so i put the 15g one on the 18t. My research points that stock wastegate pressure is at 0.3bar base and im aiming at 1.2bar. And websites recommend 1/2 target pressure for wastegate accuators so a 0.6 or 0.8bar would be better suiting sense the wastegate flapper hole is ported? Wastegate got 3mm pre tension or about half the hole where it hooks to the flapper arm. The 15g and 18t wastegates seem to be equally stiff. Right now the stock 15g is pushing 4times the spring pressure. I checked the wastegate and it does not leak both with vaccum and pressure. Right now when its acting sluggish im getting 0-60mph at around 9 seconds... Thats worse than stock listed in catalouges. Thats much info but hope you guys could help me with it and point me in a good direction without buying a new 0.6bar wastegate and wasting my money if it does not help. Thanks! Greetings from Finland!

Sommerfeldt · Post by **Sommerfeldt** » 21 May 2019, 05:51

Hey!

Standard bullet no. 1: Check your codes.

If nothing there, move on down the list.

- At 16 psi, you should probably look into a new actuator, but in all honesty, the "rating" doesn't matter much. I ran a 1 bar actuator on mine for a while, since that was all I had when I thought the original was leaking, and it was fine. Actuator is controlled by the TCV, which simply responds to what the ECU is telling it to do. If it's holding, it's holding. Check that it starts to open at around 2 psi - factory setting is 1.8. Tighten it a little if you want the boost curve to come on earlier, but be careful with that. Auto box should be building good pressures from about 2300 rpm.

I built myself an adjustment tool with hoses, a T connector, check valve and low pressure gauge (0-15 psi) to set the thing correctly, check for leaks and check full open pressure - about 25 USD total.

- Check your CBV. Mine was leaking, and I'm running a Forge piston style on mine now. A little stu-tut-tut at times, since I didn't switch to the right spring, but it works like a charm.

- Put a new Pierburg TCV in there, and see what that does, if you can. The one you have should be solid, though...

- Check your spark plug gaps and ignition components. If your gaps are off on one or more, it'll lose power in one weird way or another.

- Check that the hose from the compressor (under/left of turbo intake) is tight and not leaking. This hose creates super weird things if it leaks a little bit.

- S

Angelofhevn · Post by **Angelofhevn** » 21 May 2019, 08:11

Thanks for answering!
- No codes on the ecu.
- The Pierburg TCV from V70 phase 2 has got about 2000km on it so equal to new
- Dont know about the CBV if it seals against the turbo case but the Turbo is a replacement 18t copy that costed 420€ that i got from a swedish tuning site. 99% sure its a chinese made one. But sucking in the CBV hose or blowing tells its not leaking. Any way to see if it seals? Kinda hard spot to undo the three bolts and look under the cover. I guess i can loosen the compressor cover and rotate it so the cbv cover points upward?
- I run NGK BKR7E Copper plugs gapped at 0.4mm, New rotor and cap.
-The original 15g wastegate i dont know at what pressure it opens. Havent got a low pressure gauge to test.
- I will check the hose where turbo connects to the plumbing (the short one, about 10cm) but when i tried to pressure test the system nothing did leak. I even made a smoke machine that i used to inject smoke into the plumbing and see if it comes out somewhere but none. (only bottom of intercooler)

Im thinking to try the supplied wastegate that came with the 18t turbo. I guess the 2mm i/d barb on the wastegate should be fine with a reducer and a hose to match.
After that i will try to go to a local hardware store and see if i can gather the components for a wastegate tester.
Thanks!

Sommerfeldt · Post by **Sommerfeldt** » 21 May 2019, 09:01

Sounds like it’s wirth taking the time to check the wastegate setting.

0.4 mm sounds a little tight - is that on purpose? I gap mine to 0.6 mm - I don’t have your setup - I’m at about 0.9 bar - so I wouldn’t know.

Low pressure gauges are a bit of a hassle to find, but they’re 8 USD on eBay, and if you get the brake bleeder bottle with check valve from Biltema ( https://www.biltema.no/bil---mc/bilverk ... 2000017001 ) and a bike pump, you’re good to go. Picked up both from Biltema and put the gauge to work with a spare T-connector.

- S

Angelofhevn · Post by **Angelofhevn** » 21 May 2019, 09:09

I just bought a 100ml syringe to use as a pressure source and i will try to make a pressure tester with a gauge.
But first i will swap the wastegate and see what happends. Thanks

Angelofhevn · Post by **Angelofhevn** » 21 May 2019, 12:25

I just swapped wastegates and oh boy what a difference vs stock old wastegate! I actually answered my own question on this tropic. before it was boosting 1.2 bar and peaking 1.4 during shifts (Automatic) + the VTEC feeling at 4k rpm. Totaly gone. On the old wastegate i had 4mm pre tension now i have a total of 2 turns, about 1.5mm pre tension and boost is quick, linear and predictable! No VTEC feeling. Goes quickly to 0.7 bar at 2500rpm and as the rpms increase the boost also increases to about 3500rpm and it has a smooth sweep on the aftermarket gauge. With the new wastegate max boost is 0.9bar with 1bar at shifts but i guess its only because i got a custom tune to suit the worn wastegate and needs to be re-tweaked to suit the new. Heres a picture with the old and new wastegates and why i was worried to use the supplied wastegate that came with the turbo.

Case Closed.

Thanks!

tardcart · Post by **tardcart** » 21 May 2019, 15:59

If you look closely that's a home made restrictor shoved into the vacuum nipple,, It appears to be a piece of break line end. now I have to scratch my head as to if thats good or not. it would slow the reaction but still reach max limit of overboots. I would think it would allow boost to come on dangerously early, but maby the 18t is slow to boost and engine would be protected at low rpm by that.

Sommerfeldt · Post by **Sommerfeldt** » 21 May 2019, 21:50

tardcart wrote: ↑21 May 2019, 15:59 If you look closely that's a home made restrictor shoved into the vacuum nipple

I see why you’d think that, but I doubt it. My 1 bar Kinugawa actuator looks just like that, right out of the box.

- S

Angelofhevn · Post by **Angelofhevn** » 21 May 2019, 22:12

Nope it came like that in the box. Yep wierd! No homemade stuff here. Heres comparison stock mitsubishi and the new