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Turbo selection for 2.1L roadrace engine
I’m looking for just a bit over 500 WHP max with the best response possible since it’s for a roadrace application. Engine is an 88x88 long rod F20B running roughly 11:1 static CR with Sunoco or VP unleaded race gas only. Zero pump gas. Right now I’m running a GTX2867R so the manifold is set up for the v-band Tial housing (.86 AR). Not sure changing manifolds is in the cards right now. So let’s say I need to stick with this mani (or maybe mod the flange for a different turbo). My origjnal thought was a Gen 2 GTX3071R, but I’m wondering if I can hit my power goal without pushing the turbo to its limits. The way the race classes work is that it’s based on average dyno WHP (measured within a certain powerband around peak WHP). WTQ is not taken into consideration, so the best kind of powerband would be one where you build torque as quickly as possible (to the max WHP limit) and let torque taper off as RPMs rise so that WHP stays flat. I know this is possible with the smaller GTX2867R that I’m running now. What about the GTX3071R (.63 or .82 housing) or GTX3576R (.63 or .82 housing?). I’ve always thought the GTX35 series would be too laggy on a 2.1L, but I’ve read some pretty good stuff on the GTX3576R. Both of those would bolt up to my mani with some minor adjustments to the downpipe, intake, and hot side plumbing. Now I’d LOVE to try the G25-660, but not sure if we could easily mod the manifold to run the v-band flange for it. Downpipe and other plumbing would definitely have to change. Would love to learn more, so I’d really like to hear some recommendations and if you guys have great sources for data and info, please let me know! |
Re: Turbo selection for 2.1L roadrace engine
Let's see the dyno graph of what you have now. Not one with just power / torque, but boost pressure rpm curve. Even if it is an excel spreadsheet with the data.
you're asking something pretty specific with 3 turbo families as possibilities (GTX35,GTX30,GTX28) all you've made this pretty vague and difficult. i think you need to stay in the GT30 family, but stay on the smallest side. (You won't mac it a GTX3071 gen2 away 500 whp, I'll say that much) You need to remember that turbos actually like boost pressure, so I'm sure your limits are going to be based upon your fuel's knock resistance threshold. we'll need photos of the style exhaust manifold too. you've got a lot of information to gather up before anyone can come closer to helping you out here. You've given a lot on your purpose, which is great, but unfortunately, we'll need more. FINALLY.. A real challenge |
Re: Turbo selection for 2.1L roadrace engine
I was hoping you’d reply! Unfortunately, I’m going to make it more difficult as I don’t have any dyno data with the engine that is going to be used, as it hasn’t been installed yet. The current setup that was used for testing is a rebuilt H22A4 with stock internals. Testing was done using a 10 PSI spring on the WG (Tial MVS). It made 280 WHP on a Dynapack, but the turbo wasn’t pushed hard, of course. Everything ran great. Here are are a few pics of the manifold (the car has been built over the period of many many years!). http://www.71dsp.net//pics/preludepo...3/IMG_5509.JPG http://www.71dsp.net//pics/preludepo...3/IMG_5512.JPG http://www.71dsp.net//pics/preludepo...3/IMG_5516.JPG |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51869960)
I’m looking for just a bit over 500 WHP max with the best response possible since it’s for a roadrace application. Engine is an 88x88 long rod F20B running roughly 11:1 static CR with Sunoco or VP unleaded race gas only. Zero pump gas. Right now I’m running a GTX2867R so the manifold is set up for the v-band Tial housing (.86 AR). Not sure changing manifolds is in the cards right now. So let’s say I need to stick with this mani (or maybe mod the flange for a different turbo). My origjnal thought was a Gen 2 GTX3071R, but I’m wondering if I can hit my power goal without pushing the turbo to its limits. The way the race classes work is that it’s based on average dyno WHP (measured within a certain powerband around peak WHP). WTQ is not taken into consideration, so the best kind of powerband would be one where you build torque as quickly as possible (to the max WHP limit) and let torque taper off as RPMs rise so that WHP stays flat. I know this is possible with the smaller GTX2867R that I’m running now. What about the GTX3071R (.63 or .82 housing) or GTX3576R (.63 or .82 housing?). I’ve always thought the GTX35 series would be too laggy on a 2.1L, but I’ve read some pretty good stuff on the GTX3576R. Both of those would bolt up to my mani with some minor adjustments to the downpipe, intake, and hot side plumbing. Now I’d LOVE to try the G25-660, but not sure if we could easily mod the manifold to run the v-band flange for it. Downpipe and other plumbing would definitely have to change. Would love to learn more, so I’d really like to hear some recommendations and if you guys have great sources for data and info, please let me know! |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by Txdragon
(Post 51870114)
Is that dump tube recirced right at the downpipe elbow?!
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Re: Turbo selection for 2.1L roadrace engine
Originally Posted by TheShodan
(Post 51870015)
FINALLY.. A real challenge
Originally Posted by Txdragon
(Post 51870114)
Is that dump tube recirced right at the downpipe elbow?!
Also, I thought you said on facebook that you have a Gen2 2867 currently? The compressor housing in that pic is a first generation GTX2867r housing. The higher flow from the gen2 series is a combination of comp housing, comp wheel, and turbine wheel. Just a heads up for you. Personally, I think you're best off with a gen2 GTX3071r. I think a gen2 GTX2867r will accomplish your goals wonderfully on paper, but it's going to be running on the hotter side to do so. And considering it's a road race car that will be on and off throttle very frequently and for long periods of time, heat is not your friend. Besides, the slightly slower spool time of the 3071 (compared to 2867) may help the throttle transitions, preventing the torque thump you get from smaller turbos that can cause some nasty traction problems coming out of corners. If you'd like me to expand on this concept, I can. |
Re: Turbo selection for 2.1L roadrace engine
on second thought, another piece of info that could help the advice: What rpm are you planning to rev to? And what rpm range are you looking to have the best powerband?
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Re: Turbo selection for 2.1L roadrace engine
Originally Posted by Txdragon
(Post 51870114)
Is that dump tube recirced right at the downpipe elbow?!
Originally Posted by Caoboy
(Post 51870121)
Looks like it
Originally Posted by motoxxxman
(Post 51870142)
...you'll want to install a bellow (aka flex joint) in the dump tube between the wg and downpipe. Otherwise you run a huge risk of things cracking/warping/leaking.
http://www.71dsp.net/pics/preludepow...1/IMG_5521.jpg This guy has built many a professional race car setups, so he definitely knows what he's doing from a fabrication standpoint. I was really worried about boost creep, but he assured me that it wouldn't be an issue - and it wasn't with the 10 lb spring. Held just under 10 PSI of boost all the way to 8k RPMs.
Originally Posted by motoxxxman
(Post 51870142)
Also, I thought you said on facebook that you have a Gen2 2867 currently? The compressor housing in that pic is a first generation GTX2867r housing. The higher flow from the gen2 series is a combination of comp housing, comp wheel, and turbine wheel. Just a heads up for you.
I'd love to have a dyno plot similar to this: http://www.stratifiedauto.com/images...8Reinke%29.png See how torque comes on early then tapers off. The power curve isn't as flat as I'd want, but it's pretty darn close. The power difference in classes is pretty wide. If I build to the lower class, I only need to make 380 WHP. If I build to the higher power class, I need 520.
Originally Posted by motoxxxman
(Post 51870142)
Personally, I think you're best off with a gen2 GTX3071r. I think a gen2 GTX2867r will accomplish your goals wonderfully on paper, but it's going to be running on the hotter side to do so. And considering it's a road race car that will be on and off throttle very frequently and for long periods of time, heat is not your friend. Besides, the slightly slower spool time of the 3071 (compared to 2867) may help the throttle transitions, preventing the torque thump you get from smaller turbos that can cause some nasty traction problems coming out of corners. If you'd like me to expand on this concept, I can.
Originally Posted by motoxxxman
(Post 51870199)
on second thought, another piece of info that could help the advice: What rpm are you planning to rev to? And what rpm range are you looking to have the best powerband?
Another reason I want to keep the manifold is that I have a custom blanket already set up for it. https://www.71dsp.net/pics/preludepo...4/IMG_5320.jpg https://www.71dsp.net/pics/preludepo...4/IMG_5324.jpg |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51870218)
Yes, what's wrong with that?
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Re: Turbo selection for 2.1L roadrace engine
Originally Posted by Txdragon
(Post 51870220)
Well, I'm no engineer but everything I know about recirc dump tubes says that too close to the turbo or a 90° angle, which we seem to be presented with both in your example; causes turbulence and therefore bad for flow.
Never heard that having the recirc too close to the turbo is bad. How do internal WG turbos get around that? |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51870225)
How do internal WG turbos get around that? https://cimg9.ibsrv.net/gimg/honda-t...07b9e3f47b.jpg Somebody may offer a MUCH better explanation than I did here, but the idea is presented. |
Re: Turbo selection for 2.1L roadrace engine
Totally get that part, and the flow from the wastegate is much better than what I have since it’s parallel to the exhaust flow. No argument there. Your post mentioned the recirc being too close to the turbo outlet. An internal WG is right there with the turbo outlet so I wasn’t sure what you meant with your comment. I know the flow flow isn’t perfect on my setup, but it’s a compromise. Interested to hear other observations and learn new things! |
Re: Turbo selection for 2.1L roadrace engine
My Samsung note paint skills are lacking but this is where you'll see the biggest problems. If this particular aspect were changed alone, you could see greater gain from the turbo you're already using, at a higher psi range. It seems as if you may be experiencing troubles with your exhaust causing some unwanted disturbance to your turbine.
https://cimg3.ibsrv.net/gimg/honda-t...6bc052ec76.jpg |
Re: Turbo selection for 2.1L roadrace engine
I see no reason you can't hit close to 380 with this turbo.
https://cimg9.ibsrv.net/gimg/honda-t...b7d9a83ab7.jpg |
Re: Turbo selection for 2.1L roadrace engine
Oh I don’t think I was clear with my original post. We aren’t having any issues that I know of with the GTX2867R. It runs just fine on the current engine, but since the current engine won’t handle us pushing the turbo to its limits, it hasn’t been really tuned beyond using a 10 PSI WG spring. According to datalogs, it holds right at 10 PSI as planned. I know the 2867R won’t make it to 500 WHP. The original goal was only for 325 WHP or so. To get to 500, I figured I would need to change turbos. Unfortunately, the new engine isn’t in yet, so we don’t have any baseline to work with, and there isn’t enough time to get everything sorted with the 2867R before moving to a larger turbo. The flow issue you pointed out may be an actual problem, but we haven’t noticed yet. Maybe it’ll become an issue when we push the turbo harder. If so, we’ll have to deal with that as well. |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by Txdragon
(Post 51870236)
I see no reason you can't hit close to 380 with this turbo.
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Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51870242)
Just for clarity, is that 380WHP or 380 at the crank? I'm truly not the expert, though these are my thoughts/suggestions. |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51870238)
Oh I don’t think I was clear with my original post. We aren’t having any issues that I know of with the GTX2867R. It runs just fine on the current engine, but since the current engine won’t handle us pushing the turbo to its limits, it hasn’t been really tuned beyond using a 10 PSI WG spring. According to datalogs, it holds right at 10 PSI as planned. I know the 2867R won’t make it to 500 WHP. The original goal was only for 325 WHP or so. To get to 500, I figured I would need to change turbos. Unfortunately, the new engine isn’t in yet, so we don’t have any baseline to work with, and there isn’t enough time to get everything sorted with the 2867R before moving to a larger turbo. The flow issue you pointed out may be an actual problem, but we haven’t noticed yet. Maybe it’ll become an issue when we push the turbo harder. If so, we’ll have to deal with that as well. |
Re: Turbo selection for 2.1L roadrace engine
After reading your additions to the info, here's my advice:
use the gen1 2867 for the 380hp class. It will make it with absolutely no problem at all. use a gen2 3071 for the 520hp class. definitely run a boost control solenoid wired into the ecu for ecu controlled boost. With that, you can shape your torque curve pretty much however you want. Based on your description, you basically will want the torque curve to be flat across the board right up to your exact hp goal, then taper boost/tq off to maintain flat hp up to rev limit rpm. Pretty easy to do actually with boost by rpm. |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by Txdragon
(Post 51870233)
My Samsung note paint skills are lacking but this is where you'll see the biggest problems. If this particular aspect were changed alone, you could see greater gain from the turbo you're already using, at a higher psi range. It seems as if you may be experiencing troubles with your exhaust causing some unwanted disturbance to your turbine.
https://cimg3.ibsrv.net/gimg/honda-t...6bc052ec76.jpg |
Re: Turbo selection for 2.1L roadrace engine
I didn't think the recirc would cause a serious issue with the turbo where it is. Would moving the WG to the right a bit and merging the recirc tubing to be tangential to the downpipe make a significant improvement (like the pic)? We've already moved the alternator to the right some to get more clearance.
http://www.71dsp.net/pics/ht/IMG_5521.jpg |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51870420)
I didn't think the recirc would cause a serious issue with the turbo where it is. Would moving the WG to the right a bit and merging the recirc tubing to be tangential to the downpipe make a significant improvement (like the pic)? We've already moved the alternator to the right some to get more clearance.
http://www.71dsp.net/pics/ht/IMG_5521.jpg |
Re: Turbo selection for 2.1L roadrace engine
Ultimately, optimal placement would be quite an extensive process for your setup. It'll need to be further down past the bend, more into the straightaway. Borrowed this example from Greg @ Go-Autoworks. Hopefully he won't mind. Lol!
This is a great example of recirc placement. Why not just vent it to atmosphere though? Is there any reason it HAS to be recirc? Legend has it that there is proof in the dyno that you get better results with open vs recirc although, that could just be due to poor placement. **shrug** https://cimg7.ibsrv.net/gimg/honda-t...a4185e5c8c.jpg |
Re: Turbo selection for 2.1L roadrace engine
Doesn’t have to be recirc, but all exhaust has to exit behind the driver compartment. I can’t vent out the hood or anything like that. Packaging constraints might make running the WG plumbing that far from the turbine housing difficult. The radiator is now slanted forward a good bit, which gives more room toward the upper core support, but it didn't gain much room down low where the downpipe is. I also have to retain the OEM subframes, so using something with additional clearance around the subframe area is a no-go. |
Re: Turbo selection for 2.1L roadrace engine
Originally Posted by 117
(Post 51870448)
Doesn’t have to be recirc, but all exhaust has to exit behind the driver compartment. I can’t vent out the hood or anything like that. |
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