So I guess my Turbine wheels is fucked and needs to be replaced.

i dont know what size A/R wheel was on there before, but my engine builder now said they plan on putting a smaller wheel in there.

So my question is... if the turbo is rated to 1300rwhp or so (give or take), and I dont plan on making more then 900-1000 max rwhp, can I use a smaller A/R to increase spool and get up and go faster, or will I run into backpressure issues?

its in a 408 CI motor (might be a bit more if they rebore the block)
cam is a 236/230
6 speed setup with 3 42's.

I think right now Im at full boost around 3600-3800 with my turbo coated.

Any suggestions/opinions/input?

TIA.

 

Ok first of all, are you going with a smaller A/R turbine housing or smaller (physcially) turbine wheel??? Two different things....

Also crossing the turbine flow map of a GT55 with a 408, it needs to be NO smaller as it sits. For 1000rwhp the UHP wheel needs to stay and 1.0A/R needs to be used. You can go less, but you will have to sacrifice somewhere.

 

I think the housing is staying the same, the wheel is being replaced (as the fins were missing pieces)

 

That can't happen. If you place a smaller turbine wheel into the same housing you will have huge clearence issues and the lag will be horrible. I sure hope they aren't doing the 47 turbine with 55 housing. I have seen this before....will NOT work.

 

What would you recommend I put in? the same 55 wheel, or do you guys carry a modified wheel like the SX wheel or whatever to help increase spool and efficiency?

I guess I should find out what they plan on doing (i just assumed they are putting in a different wheel without changing the housing, but I never clarified with them).

 

I would have them put the same wheel in. Also the 47 turbine wheel is a touch small for a big 408 if you plan to make big power.

 

Sounds to me like you need to make out a list......
Then call and ask what exactly there are planning/ wanting to do.... and then go from there....

 

2000 Tran Zam, you really need to either learn more about your car or have someone you completely trust help you with the decisions, even if you have to pay them a little bit. The mistakes get costly very fast.

1. As mentioned before, boring the block out to .060 over is not a good idea unless it's checked first to make sure it will not hit a water jacket or get to thin.

2. As Nasty ta stated, you really need to make up a list and get this stuff under control, sounds like there are a lot of chef's involved in this.

3. You lost the motor once now, invest the $250 and get an aeroforcetech scan gage and set one of the parameters to monitor knock retard. If it goes over two degrees, abort your pull.

4. If you enjoy street driving and want to run 91 octane either keep the boost really low like 10-12psi or invest the $500 and get a progressive methanol kit and run a 50/50 mix of water/meth and have the car tuned for a 10.8-11.2 a/f at WOT. The meth is very cheap insurance. You live in an insanely hot climate like me, not running additional charge cooling like meth is just silly and asking for trouble. Don't use the meth to add timing or a lot of boost, use it as a safety net, that's what I do.

5. guys like you get taken advantage of pretty often by shops. Not saying anything bad about who is doing your work, but knowledge is $$$. My engine is built mostly from other peoples junk and used parts, $$$ is one way to solve problems, knowledge is the other. With all the parts, machining and assembly included, my motor cost me $3600 and I did zero labor myself. I just had good advise from someone VERY knowledgable and I paid him for his knowledge to save me money in the long run.

I hope I don't sound too much like an *** to you, but i've seen your situation many times and it has always ended with the person giving up and selling their car wondering why they just couldn't make it happen for them. The amount of knowledge you have is really what dictates how much the project will cost you in the long run.

 

+23453534598347589345

 

Well... first of all, I dont have all the knowledge and thats why I originally sent my car to Futral to build. Id say hes a pretty credible source and wealth of knowledge, and even then my motor is fucked. I didnt really trust many shops here locally with a build, and thats why I shipped it halfway across the US to a company that I thought was reputable. And believe me it wasnt cheap.

1. The shop that the car is currently at right now has done multiple FI domestic setups and is very familiar with LS1's, so I hope the knowledge they have is dependable, otherwise I dont think they would have been in business for as long as they have. If they thought the block was shot, Im sure they wouldnt put them selves in a position where they build a setup and it is fucked a few months down the road.

2. Im not sure what exactly I need a list of... I already know my power goals, have most of the parts, just trying to get opinions on a few of the options I have to the specific questions Ive asked.

3. I will agree with you here. I already have a wideband sensor but it was fucked up at the time so that had a major factor as to not letting me know I was running too lean. Had I known I would have pulled out.

4. I didnt tune the setup. When I asked for my setup to be built, it was mentioned multiple times that Id rather be down on 50-100 hp and have a setup that will live longer, as at that power level anything will still feel very fast. it was set at 12.5 lbs the first time 13.5 lbs after it was sent back again, and 15.5 or so when I pulled the exhaust (which is my fault and I cant really blame anyone else except for my friend that made a comment asking if I wanted to take it off) and thats what ultimately killed the motor. Methanol is a bandaid for a bad tune. Once again, Id rather run super conservative, be down a little bit of power, but not ever have to worry about detonating. I dont know if you've read any of my newer threads but I did mention multiple times that I plan on running 10-12 lbs on 91 and will still mix in a few gallons of 101 to be safe.

5. No matter what the situation, these cars are money pits, plain and simple, lol. The one thing Ive realized is no matter what you try to protect by buying good parts, **** happens, and parts break at this power level. Ive learned a fair amount by reading in the tech forums. Its the internet, everyone comes off as an ***, lol. But I understand your looking out for me, but its not like Im a noob or something. Its just discouraging when you put all this effort time and money into something and despite your best efforts **** still breaks.

 

Lol your one to talk, your cars been down since november!

 

Now what is big power in your mind?

I want maximum 9xx rwhp... Are you saying a 47 wheel can not supoprt 9xxrwhp via 6 speed maxed out?

I dont plan to upgrade injectors so Im limited by my fuel. So the way I figured it is make 7xx or 8xxrwhp on pump gas with some 101 for safety, and 9xx rwhp on full 101 fuel.

And I would figure with a smaller housing and wheel, it would spool faster and supply me with enough CFM to flow for 9xxrwhp.

I just dont see dropping down from a 55 to a 47 having more then 400rwhp drop potential, but if that is the case please let me know.

 

Thats because I do my own work at my own pace to make sure it gets done right

 

No it will support it, but backpressure will also be up. For example, one of our customers is running a 360ci engine. With GT47 turbine at 20psi backpressure was around 48psi. Not to good...... Now with that same unit and GT55 turbine wheel changed only he was at 38psi and 18psi and made the same power. See my point.....the setup is less stressful, more reliable and allows for better pump gas #'s.

 

I don't know why you are so against methanol, but luck in your repair, I hope you get your car back soon. Sucks to have your baby down.

Keep us updated, your threads are always enjoyable.

 

i would go with a different turbo, for one, like the S88, seems to be running well on NastyTa's car, that Gt55 isnt a good turbo for you.
methonal isnt a band-aid for a bad tune (though it can be) you could also just spray in some water in a kit for a little added cooling safety if you dont want to mess with meth.
next if you want it more reliable drop the HP output down 300rwhp or so, your setup will last longer.

 

Lol, trust me, im not taking anything away from you working on your car, as your definately more mechanically inclined then I am. However thats not the the story Ive been hearing from your brother (regarding time put into the car), haha.

 

Im not so against methonal, the Tuner is (if I remember correctly).

Plus Id rather not have to depend on it. Id rather run 6 degrees of timeing on 12 lbs making low 7xx hp and have it built into the tune then take a chance of meth failing.

But ya, my cars been down longer then its been running (since Ive had FI in it) so unfortunately and fortunately it has required me to build patience.

 

i would be satisfied with 7xxrwhp numbers on pump gas, even high 6xx's with a quicker spool.

1. lower power with a good tune should help prolong longevity correct? (assuming backpressure isnt through the wall, but I dont plan on going over 10-12 lbs 90% of the time).

2. it would be quick enough assuming I have traction, so Im willing to trade off some power for quicker spool and better throttle response (also increasing compression ratio to 9:1)

 

I would love to go with that turbo, but finances right now dont give me that option. if I have someone like psj offering me 900 for mine when market value is 2600... id rather stick with what I have and make use of it.

And like I mentioned before, Im not opposed or for meth, I am strickly going by what the Tuner has mentioned to me.

If I were to do it all over again, id probably honestly stick with a stock block running 8 lbs making around 500rwhp and save my self a ton of money, but the matter of the fact is Ive already dropped a ton into this setup and its pointless to detune an 800rwhp setup to something I could have accomplished NA.