When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Newish to the forums. Anyways, I'm a pretty big fan of Honda stuff, so I thought this would be an appropriate place to post this.
I have an idea. (that's how all evil plans start, right?)
Sorry for the crappy drawing. Used what I had available.
Single-turbo setups have one primary problem: if you want big power, you can't get it until well past 4K RPM. If you want good torque and a good around-town car, it's hard to get over 300 HP.
Sequential twin-turbo setups try to solve both of these problems. The drawbacks are turbo lag (not to be confused with boost threshold,) hard to tune, and very limited max power. (see: Toyota Supra)
Compound twin-turbo setups can provide a ridiculous amount of boost across a wide RPM range, but they too are limited, need properly sized turbos, and add a lot of unwanted backpressure.
I'm sure I'm missing some things. Feel free to chime in.
The crappy drawings I've posted above solve most of these problems. The exhaust side is set up like a typical compound system. (read: Compound turbo diesel.) The intake ditches the big turbo's straight pipe into the smaller turbo in favor of a branched off pipe with a high-flow check valve that allows incoming air to compound at low RPM, but bypass the small turbo and go straight to the intercooler at high RPM. This method allows one to swap out the small turbo for a much smaller turbo (see: Fiesta ST turbo) for an immediate high-torque punch at or below 2000 RPM. The small turbo will remain spooled until redline, but it obviously can't flow until redline. That's where the intake-side check valve and exhaust-side wastegates come in. Two paths are provided for air to flow almost entirely around the small turbo, but only after the big turbo has spooled. Speaking of the big turbo, it can be much larger than the turbo on a single-turbo setup, but simultaneously build boost much earlier due to the added boost from the very small turbo.
Got that? Okay. This design theoretically also eliminates turbo lag and boost dips. an inline 4 should feel more like an N/A V8 at anything above 2000 RPM.
Re: Sequential-Compounded hybrid for V8-like power?
From 2008-2010: This has been done, and you're idea isn't bad, just complicated.
Originally Posted by Tony the Tiger
Twin turbos will work just fine, especially with two really small turbos.
Last year I did some comparisons and the TT setup didn't spool noticeable better than a single turbo setup in parallel. I had dyno comparisons, street videos and track comparisons. I also went through two stages for this build, having both turbos spooling up in parallel, and also in sequential mode using all the OEM Toyota Supra components (ACIS, EGCV, VSV's and pressure tanks, controlled via GPO's and a PWM solenoid). A few guys here thought I was being over-creative though, but in fact, I was trying to perform a clean comparison test versus a single turbo within similar size... But it lacked interest and not many here cared about the results, so I never talked about it afterwards.
The power delivery is indeed more broad, and twin turbos rarely spool up like an on/off switch. I had a twin GT2860R setup early last year, and combined size, it is very similar to a single GT4088R by comparison. Both setups spooled up relatively the same, but the twin turbos had a softer spool up, faster torque delivery upon hitting the throttle at lower-mid RPM, but lacked the sharp response between shifts during WOT like a big single. In sequential mode, the transition was like another VTEC kick-in-the-pants, but the first turbo spooled up to 18 PSI at 3000-3500RPM and the next turbo came in at 5500RPM. However, due to boost limitations (read below), I abandoned the setup later on.
The biggest drawback for a twin turbo setup only applies to those who are pushing big power. Almost all the small turbos out there can combine as twins for lots of air flow (eg: twin GT2860R = 70 lbs/min worth of airflow), but on a small Honda engine, it needs a lot of boost pressure to push that air flow through the engine.
There are simply no small turbos out there that are sized well but still able to have a high enough pressure ratio to make use of their combined flow on a small Honda engine. My twin GT2860R setup did not work out too well because I was "boost pressure limited" to 550 WHP since the GT2860R's did not have high a enough pressure ratio to continue to make power beyond 22-23 PSI. There was enough flow for 700+ WHP, but not enough pressure to get there.
Nope, I didn't make a build thread here.. I made one on a local forum, but I basically mirrored the information on this thread anyway just now. You have all the important info here already.
If you are looking for such low power like 8-10 PSI, then it's pointless to go twin turbo. Even the stock twins off the Supra, combined, can flow for 450-480 WHP. They are already too big for your application. For 250-300 WHP, you are better off with a small single.
Building a sequential setup takes good fabrication skills, and you also need to know how to tune it as well to blend in the transition. One turbo gets full stream of exhaust, but midway, the other turbo has to "pre-spool" first before you can kick in the 2nd turbo.
Before you do anything, make sure you have a tuner that can set it up for you if you are really planning to go TT.
Think sequential...
It worked great for lower power levels (ie: 500 WHP) and under the pressure limits of the twins. If only the GT28R turbo has different wheel options suited better for higher pressure ratios, it is an unbeatable combination because you can run them to their flow limit on a Honda engine.
It managed to make 200 lbft of torque and over 18 PSI from 3200RPM and up. The sequential setup introduced another "layer" of restriction unfortunately, thus, making the turbos reach their pressure limits even sooner than expected. I was only able to top out at 500 WHP with the sequential setup. Consider that the first ever sequential TT setup ever on a Honda.
You will never find a single turbo that can match the low-end and midrange spool and still have the flow capability for 500 WHP on a 1.8L GSR versus a sequential twin turbo setup. It's more than just being unique if you understand benefits of the system and know how to set it up.
I definitely scored a lot of points when I had the TT setup as well... So many guys at the local meets were in total shock that I could fry my tires with smoke in 2nd gear from a roll but 500WHP on tap. But you know, it gets old after a few months, and I was a happier person with 650+ WHP and trying to score 140+ mph traps on street tires and pump gas instead...lol
Divided scroll is nowhere near close to twin turbo in terms of reducing lag. I have a "twin-scroll" (real correct term is divided-scroll -- courtesy of TheShodan) setup right now, and yes, it helps spool quite nicely but not like a TT setup though.
Re: Sequential-Compounded hybrid for V8-like power?
This isn't quite a sequential setup, though it is similar. It's also similar to a compound setup. Engineering Explained did a video a couple of years ago on "Twin turbo diesels". he laid out the same setup as I have mentioned here, that would probably make more sense than my crappy drawings and explanations.
I've realized a potential issue when involving a smaller small turbocharger, and I'm not entirely sure on the best method to solve it.
The small turbo is going to die off by around 5000-ish RPM, assuming a turbo from a vehicle such as a Fiesta ST is used. anything under about 4500 RPM is going to spool pretty much instantly, but problems are going to pop up when over the limits of the small turbo, as there will be enough exhaust volume to spool the big turbo, but not enough pressure to open the wastegate(s) on the small turbo to bypass the restrictive small turbo. this would result in very high backpressure when trying to spool over 5K RPM (trying to spool at 2-4K RPM would not have this issue), which would result in detonation or other problems.
If a 7 PSI spring is used in the wastegates for the small turbo, the turbo should be able to pull all the way to redline with the wastegates open. The problem is that now it's running a lower than optimal boost in it's highest efficiency range. You can use a manual boost controller hooked up to the wastegates on the small turbo to push, say, 15 PSI of boost, but again, the wastegates will not open after the optimal range is passed. an electronically controlled valve could run in parallel with the boost controller and be wired to only open above 5000 RPM, bypassing the boost controller and running wastegate pressure. This would put the small turbo back in it's optimal efficiency range under the condition of spooling over 5000 RPM, opening the wastegates and allowing the whole engine to breathe easier and the big turbo to spool much faster. (am I rambling here?)
How this switch would be wired in, I'm not entirely sure. This concept would be a PITA to tune too, though it would be sick for a street car.
Re: Sequential-Compounded hybrid for V8-like power?
I believe youre kinda overthinking this.But here it is:
Once the small turbo with lets say 15 psi wastegate sees 15psi on the plenum the wastegate will open. Once its open the gases from the small turbo and the gases that are bypass will be equalised on the two paths reducing back pressure and
the heavy load the turbo had, because the big turbo is now spooled it presses the air into the small turbo inlet helping the turbo rotate(the turbo will still work). The big turbo's see boost from the intermediate pipe.If the big turbo pushes 7psi and the small turbo needs 15 psi for its wastegate to open then half the psi are allready provided by the big turbo.So the small turbo will work to produce only 4-5 psi(1,35 pressure ratio) that are multiplied with the 7 psi ( 1.5 pressure ratio) the big turbo provides to give a result of pressure ratio 2, AKA 15 psi.
If you really need the gasses to bypass the small turbo completely you can put a small 10psi wastegate on the small turbo and a lets say 25 psi wastegate on the big turbo.
This way because the big turbo will provide both boost targets the small turbo wastegate will be open 100% once the big turbo is spooled. But im not sure how much speed the small turbo will have. It may rotate TOO FAST that will get fucked. Because the moment you free the small turbo from producing boost is like taking a brake from it. The big cfm from the big turbo wont help either. Id like to see turbo rpm measured for this.
Re: Sequential-Compounded hybrid for V8-like power?
I'm too lazy to look right now, but there is a guy on s2ki who has a twin scroll EFR (forgot what size) s2000 compounded by an s475?sxe (iirc). He posted the graphs and the thing is a complete monster, and he's at around 900whp iirc.
The thing about these setups is that people apparently don't like "over-complicating" things. Sure, it's more costly, requires more fabrication and tuning, however I think the benefits are definitely worth it. I'm hoping to attempt a conventional compound setup myself in the next year or so, except it's going to be with a rear-mounted secondary turbo
*edit* "But im not sure how much speed the small turbo will have. It may rotate TOO FAST that will get fucked. Because the moment you free the small turbo from producing boost is like taking a brake from it. The big cfm from the big turbo wont help either. Id like to see turbo rpm measured for this."
That's an interesting point that needs to be taken into consideration. Perhaps he can add a restrictor to the charge piping on the primary turbo that is actuated?
This is complete theory on my end, but it seems logical to me that having a sidewinder manifold for optimal top-end flow along with exceptional wg flow would be a good idea for this setup. Thoughts?
Re: Sequential-Compounded hybrid for V8-like power?
Originally Posted by Geis
I'm too lazy to look right now, but there is a guy on s2ki who has a twin scroll EFR (forgot what size) s2000 compounded by an s475?sxe (iirc). He posted the graphs and the thing is a complete monster, and he's at around 900whp iirc.
The thing about these setups is that people apparently don't like "over-complicating" things. Sure, it's more costly, requires more fabrication and tuning, however I think the benefits are definitely worth it. I'm hoping to attempt a conventional compound setup myself in the next year or so, except it's going to be with a rear-mounted secondary turbo
Re: Sequential-Compounded hybrid for V8-like power?
Originally Posted by Geis
I'm too lazy to look right now, but there is a guy on s2ki who has a twin scroll EFR (forgot what size) s2000 compounded by an s475?sxe (iirc). He posted the graphs and the thing is a complete monster, and he's at around 900whp iirc.
Pardon me for mis-remembering, he still hasn't had the setup completely dialed in. Close to around 600whp on a mustang dyno, with 300wtq @3500 rpm...if that doesn't prove the potency of compound setups, I don't know what would.
Re: Sequential-Compounded hybrid for V8-like power?
I need to learn how to read compressor maps. :S
#CompoundMasterRace
The ridiculous power band and boost levels of compound setups makes me wonder why they're not more common.
After thinking about it a bit, I've realized that the resulting pressure ratios at each stage are going to vary by RPM, depending on each turbo's efficiency of course. turbo choice matters more than anything. Too big of a difference between turbo sizes and the second stage will choke the first stage at high RPM. Too small of a difference and you won't see any benefits of compound setups. There's a sweet spot somewhere in there, and it depends on the compressor maps.
Still overthinking it...
Using a very small small side turbo would limit maximum boost and lower efficiency, but running, say, 20 PSI of boost is plenty for most motors, and running 15 PSI of boost by 2000 RPM and 20 PSI from 3000-8000/9000 means that almost all of your powerband is completely usable. Like a big, high revving V8. The big thing hondas lack is usable torque, right?
Re: Sequential-Compounded hybrid for V8-like power?
Here is a successful compound turbo setup on a 2G DSM. If you pause on certain parts of the video you can get a closer look at the plumbing.
I believe this setup uses a TD04 or TD05 primary with a GT42 sized Forced Performance turbo as second stage.
Edit from a compound turbo Pontiac Solstice: - Kevin Jewer – owner of 1991 Eagle Talon compound turbo set-up (T3 50 trim and T6 s475 w/ 1.06 AR) – 8.97sec @ 156mph Thank you for all the step-by-step answers that you provided me!!! You have been my on-line mentor!!!
Re: Sequential-Compounded hybrid for V8-like power?
Originally Posted by DeSerees
I need to learn how to read compressor maps. :S
#CompoundMasterRace
The ridiculous power band and boost levels of compound setups makes me wonder why they're not more common.
After thinking about it a bit, I've realized that the resulting pressure ratios at each stage are going to vary by RPM, depending on each turbo's efficiency of course. turbo choice matters more than anything. Too big of a difference between turbo sizes and the second stage will choke the first stage at high RPM. Too small of a difference and you won't see any benefits of compound setups. There's a sweet spot somewhere in there, and it depends on the compressor maps.
Still overthinking it...
Using a very small small side turbo would limit maximum boost and lower efficiency, but running, say, 20 PSI of boost is plenty for most motors, and running 15 PSI of boost by 2000 RPM and 20 PSI from 3000-8000/9000 means that almost all of your powerband is completely usable. Like a big, high revving V8. The big thing hondas lack is usable torque, right?
If you have a big wastegate to bypass the small turbo and feed the big turbo (id use 60mm) you wont have problem on the hot side.
On the cold side i dont think youll have a big problem, unless you ask too much work from the small turbo. What i mean and its kinda difficult to undestand:
Lets say your small turbo wastegate is 22psi.And as a large turbo you picked a 60-1 (thats actualy a really nice low psi turbo for this setup) and you set the big turbo to 5 psi.
You are at 2000 rpm and you step on the gas. The exhaust gases accelerate the small turbo until the wastegate sees 22 psi. Thewastegate cracks open wasgating the gases to feed the big turbo.
The moment the big turbo creates 5 psi the pressure in the plenum is ~ 35psi.Well this will never happen because now the wastegate will open 100% since the big wastegate want to hit 22 psi target.
This means every psi the big turbo creates the small turbo wastegate will open more not to over boost. The small turbo final compression ratio will be 1,9 bar or 0.9 bar boost or ~13 psi boost.
Again it will work at 13 psi so the final target is 22 psi.
Here comes the magic. That 13 psi will require much more energy than a normal setup with that turbo at 13 psi. Because it compresses DENSER air. More work required = more energy stolen from the more efficient big turbo.
The good thin is that altho it compresses denser air, this denser air has kinetic energy and comes "boosted" so it helps it spin. But again im talking about taking boost target for the big turbo from the intermediate pipe so if the small turbo has a big problem swallowing that air=
the big turbo hits its target too quick because of the swallowing problems.
The theory is ver very deep and complicated i spent a lot of time reading about compounts some years ago.
The real problem is how changing boost sources and pressure combination affects the final result and i never found that data.
Re: Sequential-Compounded hybrid for V8-like power?
I agree with Teg here, compound/sequential systems are very complicated. With not many gains to be had, there have been some successful applications out there but if it was so great I feel like there would be many more of them out there.
IMO your better off doing a single with a properly sized turbo
Re: Sequential-Compounded hybrid for V8-like power?
I have looked into compound and understand how to set it up pretty well. Issue with compound is sizing the turbos approprietly and unless you are looking for over 1000whp the performance increase is not that big. Then again i guess it depends on what type of racing you are doing.
Re: Sequential-Compounded hybrid for V8-like power?
bmw n20 engines are 2.0 like all german cars that are 2.0 turbo come with compound turbos. n20 engines also have valvetronic, vanos (vtec and vtc?) and variable intake manifolds and there still lag.
01-08-2018, 02:54 PM
Sequential-Compounded hybrid for V8-like power?
Re: Sequential-Compounded hybrid for V8-like power?
