Sizing a turbo

[Rookie2]

I'd be interested in hearing peoples opinions (pros and cons) regarding what is best RPM to have the turbo spool up. Am I understanding the graphs above correctly, this turbo doesn't spool until about 2600 rpm?

Thanks
Rookie2

 

[sleeoffroad]

The setup is for highway cruising. It has great throttle response at 65+ mph and offers excellent cruising and overtaking capability.

The reason that graphs start that late is that we can not get it to not downshift if we start the WOT run earlier.

At 2600 rpm you already have about 40hp more than stock.

I do believe the Safari spools up faster, but it does not have the top end that this setup has.

Also important to note that this is wheel horsepower measured on a 4wd dyno.

 

[sleeoffroad]

For comparison, here is the same graph with a dyno run of a 93 Supercharged truck.

 

[sleeoffroad]

Rick, fwiw, the turbo that AVO uses is GT40-35

 

[concretejungle]

so in the above graph, the only real difference is the SC is not intercooled and the turbo is?

 

[SUMOTOY]

For comparison, here is the same graph with a dyno run of a 93 Supercharged truck.

Might be interesting to see what really happens below 2600. Might also be interesting to see the 'Carb compliant' 4.5psi boosted Safari dynos at.

Christo, I presume you to be using a To4 trim Garrett, as does Dusty, as do others. Without giving away the store, how does your turbo trim compare to Dusty's? Is yours oil only Garrett or oil water?

ST

 

[clownmidget]

Scott - post #64. You should try reading.

The Kazuma/TRD s/c also has similar restrictions for CARB compliance/exclusion. What happened to your "lb boost for lb boost" comparo?

 

[Dusty]

Im using a cheap ebay remote wastegate currently running a 6lb spring. It has provisions for remote boost regulation but I'm not using that. I spent over a grand but less than two on the project. I easily should have paid myself $5000 for labor.

My set up removes vacume at lower rpms but isn't realy starting to boost till 2000+ rpms. As is the case for Christo, my turbo is also for the highway. Im not doing getting 8psi at only 2600 rpms as illuded to earlier. My booste doesn't pass 6psi unlesss Im really loading the motor (going up mountain) and well into 3000/4000 rpms. My gauge has never seen past 8psi. (unless the wife is mudding it hard without me knowing)

 

[sleeoffroad]

so in the above graph, the only real difference is the SC is not intercooled and the turbo is?

It wasn't on the same truck. In another thread I posted the stock vs turbo vs supercharger for that specific truck. It was a 93 with different fuel system than the 97.

Turbo system is intercooled and uses 2 additional injectors and tunable piggy back computer.

Turbo is oil and water cooled.

We are not that worried about the lower RPM's. Where do you ever drive these trucks at 2000 rpm on the road? I know a lot of people will look at the curves and go, " Hey the power comes on to late". However try driving one of these trucks on the road, and you will be surprised at how well it works. It feels like a big block.

I would love to get turbocruisers truck on the dyno. He just needs to say when we need to meet there.

As for the CARB compliance, if you start modifying the SC, you loose that as well. I guarantee if you add a intercooler and get denser air, you are going to need more fuel as well.

 

[reffug]

I'm right there with Turbocruiser................

I'm running mine now in the 7/8 lb boost range.

Got a little bit of power.

 

[Rookie2]

However try driving one of these trucks on the road, and you will be surprised at how well it works. It feels like a big block.

So you still get some "off the line" umfff?? Otherwise it would seem like a lot of money to spend to get better 65+ mph response.

Thanks for the education.
Rookie2

 

[landtank]

Rick, fwiw, the turbo that AVO uses is GT40-35

Thanks Christo but I really didn't expect this. I'm not here expecting anyone to help me and others out in this while cutting their own throats.

 

[sleeoffroad]

You got to remember that this is a run done in third gear. Next time you accelerate watch your RPM's. Very simplistic, remember you get the boost in all the gears at the given RPM band.

Also, we are not recording these runs to prove the turbo works, we are tuning the vehicle to have proper fuelling. If we had the dyno here at the shop, we could do much more, but we pay by the hour to use the dyno.

Look at it this way, on the top run, you have about 85 wheel hp at 2600 rpm. With the turbo you have about 120 wheel hp. That is a 40% increase at 2600 hp.

 

[sleeoffroad]

Thanks Christo but I really didn't expect this. I'm not here expecting anyone to help me and others out in this while cutting their own throats.

Rick, it really doesn't matter. AVO does not mind to share the info. The turbo selection is a small part of the equation. Making the parts and doing the castings etc etc is where the money comes in.

 

[SUMOTOY]

Scott - post #64. You should try reading.

That's AVO using a GT40-35 turbo? I'd expect that to be a late bloomer on a 4.5l 6.

The Kazuma/TRD s/c also has similar restrictions for CARB compliance/exclusion. What happened to your "lb boost for lb boost" comparo?

Er, happy to do one or the other. Christo has pointed out his comparo is a kit as out of the box delivered, hence why he didn't have a intercooler on the SC comparo. From Carb D490, the comparo should be 4.5psi on the Safari.

I guess to state the obvious for you: Is the Safari kit that you recieve with the Carb compliance sticker, really Carb compliant? Not if it exceeds 4.5psi. The TRD is at 6.5psi.

Now, since I've already baselined my fuel on the SC, there is no question in my mind that additional fuel can be added to the SC and still stay well within the bounds of CVS-75 test procedures as I understand them. I suspect Toyota didn't do this because of cost of kit, but HC emissions on the SC kit has a lot of room to move, and most likely improve Nox and CO. Also, since intercoolers don't change airflow, only air density, those are pretty easy to keep Carb compliant. As a rule, it's the flow that kills Carb exemptions.

As a rule, Carb also likes SC's, because they clamp down on variance by pulley diameter and crank diameter (for example, the TRD kit EO has 3.2in pulley and 7.7 crank pulley defined). As a rule, they don't like turbos, cuz it's too easy to crank boost, it's easy to mod any given turbocharger unit, all using the same defined hair drier.

I also did a quick revisit of my notes vs available turbos on a single turbo applied to the 80. Not much has changed, the biggest problem is finding good compressor efficiency and speed at really low pressure ratios, then not choking the exhaust flow. Finding a turbo that works well at 2-3PR is easy.

I only see one Garrett that appears to be a good fit to the 1FEFZ motor. I also suspect there aren't many that are going to show boost improvements below 2600rpm without choking or surging.

After that revisit, Istill come to the same conclusion that a single turbo isn't *better* than the SC in a intercooled kit at the same boost, only *different*.

That GT-28RS still looks really good for twinsies tho! Come on Dusty, it's time to plug that welder in and go dual water cooled ball bearing man!

ST

 

[sleeoffroad]

After that revisit, Istill come to the same conclusion that a single turbo isn't *better* than the SC in a intercooled kit at the same boost, only *different*.

After driving them both, I am still convinced the turbo is better.

 

[SUMOTOY]

Im using a cheap ebay remote wastegate currently running a 6lb spring. It has provisions for remote boost regulation but I'm not using that. I spent over a grand but less than two on the project. I easily should have paid myself $5000 for labor.

Dusty:
I suspected as much. With external wastegates especially, you can get a lot of wastegate creep (a major issue that Corky doesn't cover well IMO). What happens is you get a surge of boost causing the WG to open, then spring pressure trying to clamp it back down, you lose a lot of low end torque this way. Much worse on oversize turbos as well...

The best way to address it is with a boost controller. A simple one like the Profec B is my favorite, the more complicated ones just have fuzzy logic that can create more problems than solve.

You should end up with a much better boost ramp profile, though somewhat offset by surge line hits at low boost levels on that turbo you have. If you want to change this over to your well documented turbo install thread, I can do so. It doesn't hurt here, it's just premature right now....

HTH

SJ

 

[SUMOTOY]

After driving them both, I am still convinced the turbo is better.

Christo, have you driven the SC with intercooler and correct fueling?

SJ

 

[landtank]

Well one mystery solved for me. I kept reading T3 flanged turbos for this truck as well as the above calculator calling out for a smaller than T4 flanged turbo.

On the drive in this morning I had an epiphany of sorts. I realised that there was no place to select the engines configuration. So assuming that the calculator would assume that a displacement of 4.5l would be in a V configuration and size the turbo accordingly (one side of the engine), I doubled the displacement (actually went to the max) and it called for a GT42.

Not a revelation I'm sure to a few but in case someone of my similar inexperience has noticed the same discrepancy this is what it is.


Here is a site that I found for various MAPS

 

[SUMOTOY]

Well one mystery solved for me. I kept reading T3 flanged turbos for this truck as well as the above calculator calling out for a smaller than T4 flanged turbo.

On the drive in this morning I had an epiphany of sorts. I realised that there was no place to select the engines configuration. So assuming that the calculator would assume that a displacement of 4.5l would be in a V configuration and size the turbo accordingly (one side of the engine), I doubled the displacement (actually went to the max) and it called for a GT42.

Not a revelation I'm sure to a few but in case someone of my similar inexperience has noticed the same discrepancy this is what it is.

Rick:
All calculators assume 1 turbo per given displacement. For dual turbo systems, you just plug in half the engine displacement and half the calculated baseline airflow (same PR).

Did you get an airflow number in lbs/min you are targetting yet?

SJ