Engine/Transmission (1998.5 - 2002) Wastegate mods

[DNewell]

In another forum here on TDR, someone was indicating that I can alter my wastegate to run slightly higher boost pressures. Does anyone know how this is done, and if so, if this is a bad idea? I'm concerned that if by running higher boost pressures, it will eat up the stock HX35 Holset. Has anyone done this with their trucks and had problems, or anything good come about out of it? I'd be curious to find out.

 

[SnoKing]

In another forum here on TDR, someone was indicating that I can alter my wastegate to run slightly higher boost pressures. Does anyone know how this is done, and if so, if this is a bad idea? I'm concerned that if by running higher boost pressures, it will eat up the stock HX35 Holset. Has anyone done this with their trucks and had problems, or anything good come about out of it? I'd be curious to find out.

Does the van Aaken V5 (Box?) have a boost fooler included? If so you then need an adjustable boost elbow. Set it to around 29-30 lbs and you will not hurt the turbo. SNOKING

 

[Joe Mc]

Remember - More pressure doesn't mean more volume just hotter air to be cooled in the intercooler - see issue 54, I think page 128 give the details. Just came today.

 

[NoSeeUm]

In another forum here on TDR, someone was indicating that I can alter my wastegate to run slightly higher boost pressures. Does anyone know how this is done, and if so, if this is a bad idea? I'm concerned that if by running higher boost pressures, it will eat up the stock HX35 Holset. Has anyone done this with their trucks and had problems, or anything good come about out of it? I'd be curious to find out.

Most would say that 35 psi boost is max for a HX35 at sea level. Depending upon your altitude that pressure would need to be lowered some what.



Above that, as Joe already mentioned, the compressor efficientcy drops and you start heating the air an extreme amount for a small increase in pressure. The upper boost pressue is based upon that which is also essentially the upper RPM limit of the turbo.



Jim

 

[JBrewton]

I'm just have a larger boost elbow. I'm getting 40lbs. of boost and temeratures are staying good.

 

[PC12Driver]

Whoa... 40psi out of a HX35 probably means something like 70+psi drive pressure. Headgaskets don't like that. And also consider that you're only wastegating 3 of the 6 cylinders, so who knows what's happening to the ungated half (egt/pressure-wise). Bad, bad, bad...



Ever notice that the egt needle speeds up once you pass 35 psi or so? Get your boost back down to 30-35 and you'll be much better off.

 

[DNewell]

Okay, so the consensus is that I can get higher boost from the HX35, because based upon all info I see, factory they should be maxing out at like 23psi. I saw an ad in the classified's section where someone was selling adjustable NPT elbow fittings that you can alter the amount of air that comes off the turbo that is sent to the wastegate to open the valve. Is this an alternative fix? I'm figuring that I can go to a plumbing supply store and find the same thing for quite a bit less than what this part was being sold for. Otherwise, where would I find a boost elbow? I'm so new to this stuff, that I don't know a lot about some of these options. Thanks guys!

 

[SKneeland]

go buy an 1/8"NPT needle valve and whatever you need to reconnect the hose to the valve.

screw the valve into the turbo housing, attach the hose to the valve, punch a small hole in the hose.



theres your adjustable wastegate



ask yourself what do you need the extra boost for?

if you dont have a boost fooler or a chip/box with that feature your truck will defuel when it sees over 21psi of boost anyway. i believe the stock hx35 is good for 30-35psi max? anything more than that is wrecking your turbo and just heating the air.



boost alone wont make you HP... .

 

[analog]

Whoa... 40psi out of a HX35 probably means something like 70+psi drive pressure. Headgaskets don't like that. And also consider that you're only wastegating 3 of the 6 cylinders, so who knows what's happening to the ungated half (egt/pressure-wise). Bad, bad, bad...

Can someone explain this a little more to me?



First, how does 40 psi turn into 70+psi in the intake?



Secondly, I always thought that wastegate controlled what came out of the turbo, how is that only affecting 3 cylinders?



Help a newb out here!

 

[darkhorse]

Can someone explain this a little more to me?



First, how does 40 psi turn into 70+psi in the intake?



Secondly, I always thought that wastegate controlled what came out of the turbo, how is that only affecting 3 cylinders?



Help a newb out here!

Because, on the Holset unit, the wastegate is on only one volute of the turbine housing, some people feel only 3 cylinders are gated. Think about this, both volutes combine just a couple of inches further down stream, so less volume from one volute means there is more room for the other to exit. The total volume of exhaust gass going through the turbine wheel is therefor reduced.

 

[PC12Driver]

First, how does 40 psi turn into 70+psi in the intake?

Not in the intake, in the exhaust manifold (drive pressure = the pressure in the exhaust manifold driving the turbo). The overspeeding exhaust turbine creates a restriction to airflow. So you end up with substantially more pressure on the exhaust side of the engine than on the intake.

 

[JBrewton]

so I need to watch it if I'm building 40 psi boost. What will a bigger turbo housing do for me?

 

[SKneeland]

so I need to watch it if I'm building 40 psi boost. What will a bigger turbo housing do for me?

more lag, lower EGTs on the top end, but can lead to higher EGT waiting for the turbo to spool up

 

[NoSeeUm]

Whoa... 40psi out of a HX35 probably means something like 70+psi drive pressure. Headgaskets don't like that. And also consider that you're only wastegating 3 of the 6 cylinders, so who knows what's happening to the ungated half (egt/pressure-wise). Bad, bad, bad...



Ever notice that the egt needle speeds up once you pass 35 psi or so? Get your boost back down to 30-35 and you'll be much better off.

I hard pegged the needle on my 60 psi drive pressure gauge at 35 psi boost. This is probably more than hard exhaust braking, but its to tell for sure with the needle jumping so radically. I believe 60 psi is the max the brake is designed to hold up.



Jim

 

[PC12Driver]

I hard pegged the needle on my 60 psi drive pressure gauge at 35 psi boost. This is probably more than hard exhaust braking, but its to tell for sure with the needle jumping so radically. I believe 60 psi is the max the brake is designed to hold up.



Jim

Good point. Exhaust brakes shouldn't create more than 60psi of backpressure. Above that the pressure can hold the exhaust valves open.

 

[DNewell]

go buy an 1/8"NPT needle valve and whatever you need to reconnect the hose to the valve.

screw the valve into the turbo housing, attach the hose to the valve, punch a small hole in the hose.



theres your adjustable wastegate



ask yourself what do you need the extra boost for?

if you dont have a boost fooler or a chip/box with that feature your truck will defuel when it sees over 21psi of boost anyway. i believe the stock hx35 is good for 30-35psi max? anything more than that is wrecking your turbo and just heating the air.



boost alone wont make you HP... .

I'm not trying to develop more HP from the engine. My alterior motive is to get more boost to help with additional fueling. I have a chip with a boost fooler, so it should continue to add fuel over 21psi. I was thinking about getting bigger injectors, and on the other posting, everyone indicates that I need to get a bigger turbo if I go with bigger injectors. If I can develop more boost out of my stocker turbo, without going too radical, then I can add more fuel. I was thinking of adding some RV275 injectors(basically 60-75hp), but everyone else is thinking that my EGT's would raise too high and melt the motor and turbo down if I'm not running some additional boost. My budget will not allow a bigger turbo AND bigger sticks. If our stocker turbos are good for 30-35psi, this, from what I'm learning, should be more than adequate for an additional 60-75hp. If someone can correct my logic(or lack thereof), I would appreciate it. If I am correct, this would be a reasonable way to get a little more performance with stock components. I'm trying to keep the stock turbo because I'm wanting to add an exhaust brake, and with the HX40, my understanding is that there are major modifications that are required to put a brake behind this.

 

[SKneeland]

the rv275 injectors will work nice with the hx35. i think i ran DD jammer 3s(100hp) on my 01 with the stock turbo for a while before i changed i out for bigger.

 

[analog]

Because, on the Holset unit, the wastegate is on only one volute of the turbine housing, some people feel only 3 cylinders are gated. Think about this, both volutes combine just a couple of inches further down stream, so less volume from one volute means there is more room for the other to exit. The total volume of exhaust gass going through the turbine wheel is therefor reduced.

Not in the intake, in the exhaust manifold (drive pressure = the pressure in the exhaust manifold driving the turbo). The overspeeding exhaust turbine creates a restriction to airflow. So you end up with substantially more pressure on the exhaust side of the engine than on the intake.

Thanks for the further explanation guys. I'm learning slowly but surely.