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Anyone experience terrible boost creep on the 13c?

iHateVolvoPeople

Active member
Joined
Feb 1, 2014
Location
Midwest
93 244+T, LH2.4, 2.5" straightpipe, iPd turbo cam, m47

I've noticed that with my 13c, especially in the colder weather, the boost creep is terrible. I can feel the wastegate open at the desired 7psi but if I lay on it and wrap out a gear it will spike to 10-11psi.

I have my MBC set to about 10 psi and it creeped to almost 15psi as I approached 5k so I had to feather the throttle to avoid knock.

My 'theory' behind this is that the wastegate hole is much too small to evacuate sufficient exhaust gasses to regulate boost levels. I haven't taken measurements, but the puck is of adequate size. Underneath the puck, however, is MUCH smaller than the puck. I'm assuming if I were to port this hole to be a similar size to that of a 15g, the creep would go away. I had no spike on my 15g.

Anyone else experience this?
 
Waaay back in the day I broke my M47 on the first really crisp fall day. I'd been hammering it all summer, no issues. Some cold air, a little boost spike, and 3rd gear disappeared into bits.
 
I half ass ported the wastegate hole with some $13 Amazon carbide burrs and it's much better. The roads are wet so I'm having trouble keeping traction and bringing it up towards redline in second.

Will see how it maintains boost when the roads are dry and I can get traction.
 
I bought a modified wastegate that was worked on for flow long ago from cherry turbos. This was for a T3. He told me at that time that if the modified wastegate didn't fix my boost creep then the next step was to enlarge the port in the turbine. Fortunately it did.

Or you can update to a larger turbine pretty reasonable with a mitsu turbo. Like the turbo from the 850 people use here. 15g I think.
 
I bought a modified wastegate that was worked on for flow long ago from cherry turbos. This was for a T3. He told me at that time that if the modified wastegate didn't fix my boost creep then the next step was to enlarge the port in the turbine. Fortunately it did.

Or you can update to a larger turbine pretty reasonable with a mitsu turbo. Like the turbo from the 850 people use here. 15g I think.

Good info here. Cherry turbos made the wastegate, link?

Update again: did a 2nd gear pull to redline and it still creeped to 13psi.

I know this 13c is small and useless for power, but it is in near new condition. No play, no smoke, nothing. I keep it on here for reliability.

Would a bigger turbine wheel cause it to creep less?
 
Would a bigger turbine wheel cause it to creep less?

Yes. Although a more general answer is that a higher flowing turbine will reduce creep, so either a larger turbine housing A/R or a wheel that flows more with an appropriate housing. Higher flow can be due to larger wheel inducer diameter, larger trim, aerodynamic design, or a combination thereof. You can use turbine maps to gage the flow capacity.

Higher turbine flow means less wastegate flow is needed to maintain the same boost pressure, assuming the compressor is unchanged. Your wastegate is choking, meaning you either need a higher flowing wastegate orifice or a higher flowing turbine that consumes more flow to get to the same shaft speed thereby reducing the required wastegate flow.

You can also just make your post-turbine exhaust more restrictive! Or port the crap out of the turbine housing inlet and wastegate passage. :)
 
Yes. Although a more general answer is that a higher flowing turbine will reduce creep, so either a larger turbine housing A/R or a wheel that flows more with an appropriate housing. Higher flow can be due to larger wheel inducer diameter, larger trim, aerodynamic design, or a combination thereof. You can use turbine maps to gage the flow capacity.

Higher turbine flow means less wastegate flow is needed to maintain the same boost pressure, assuming the compressor is unchanged. Your wastegate is choking, meaning you either need a higher flowing wastegate orifice or a higher flowing turbine that consumes more flow to get to the same shaft speed thereby reducing the required wastegate flow.

You can also just make your post-turbine exhaust more restrictive! Or port the crap out of the turbine housing inlet and wastegate passage. :)

All good info above! Thanks. As for the bolded section, that's kind of what I did. I ported the wastegate area a reasonable amount, but the problem persists. I'm sure I could port it more heavily, but it was my first time ever using a die grinder and carbide burrs. I will upload a picture so everyone can laugh:lol:

Making the exhaust more restrictive should always be a no-go I thought. Yes it will help control boost levels, but surely it will hurt performance? It's a 2.5" straight pipe to a straight through ultra quiet resonator.
 
I enlarged the wastegate hole on my 13c with a 3/4in drill (pretty sure that was the size), and then a bit more with carbide burs. I then made a nice entry way to help the exhaust gases make the 90deg turn into it. I minimally ported the inlet to the turbine housing, and then matched up the manifold. It's rock steady at stock boost to 15psi... well mostly rock steady. I get about 1psi of boost creep....

Engine is a b230ft with a 2.5in exhaust, so you'll probably have a bit more exhaust energy from the higher compression pistons.
 
I enlarged the wastegate hole on my 13c with a 3/4in drill (pretty sure that was the size), and then a bit more with carbide burs. I then made a nice entry way to help the exhaust gases make the 90deg turn into it. I minimally ported the inlet to the turbine housing, and then matched up the manifold. It's rock steady at stock boost to 15psi... well mostly rock steady. I get about 1psi of boost creep....

Engine is a b230ft with a 2.5in exhaust, so you'll probably have a bit more exhaust energy from the higher compression pistons.

I was pretty conservative with the burrs, maybe I should open it up a bit more? Worst case I'm out a $60 turbo.
 
Have you it’s ever noticed how hilariously small the wastegate hole on a 13c is in comparison to the actual size of the puck? It’s nearly half the size.

Then if you look at an hl turbo like the 13g/15g, they’re much much bigger. I’m tempted to install this 13g but do not have a proper wastegate bracket. I’m almost positive that the larger wastegate would keep boost more steady.

I could also go at the 13c hotside a little more with the carbide burrs. I initially feared ****ing it up but I’m not too worried anymore.

Anyone have pictures of their ported td04s? id like to see how much I can take off.
 
Mine definitely creeps if i'm in boost for more than 15 seconds. I loosened my waste gate a little and it helped a tiny bit
 
Mine definitely creeps if i'm in boost for more than 15 seconds. I loosened my waste gate a little and it helped a tiny bit

There?s no preload adjustment on a 13c. Not on mine at least. I don?t think it?s an issue of opening far enough, but that the hole is simply too small.
 
I'm running a Kinugawa actuator set to about 7-8psi. No boost creep that I've noticed.

I did, for giggles, try shimming the factory waste gate with a couple washers. I got a one or two extra psi over the 5psi opening pressure, but it kept the actuator arm from opening the waste gate fully, so there was crazy boost creep! A couple mm made all the difference.

I have a spare Kinugawa actuator arm here. I could see if it has more travel than the factory arm. Maybe that's part of the restriction?

-Ryan
 
I'm running a Kinugawa actuator set to about 7-8psi. No boost creep that I've noticed.

I did, for giggles, try shimming the factory waste gate with a couple washers. I got a one or two extra psi over the 5psi opening pressure, but it kept the actuator arm from opening the waste gate fully, so there was crazy boost creep! A couple mm made all the difference.

I have a spare Kinugawa actuator arm here. I could see if it has more travel than the factory arm. Maybe that's part of the restriction?

-Ryan
It could be. I really just attributed it to the small hole. But who knows; it may not be opening far enough.

If you don't mind having a look that would be awesome.
 
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