12a CarTech drawthrough HELP!!
02-02-09, 01:21 AM
#52
I've recently been PMing someone who is reminding me the original CarTech installation instructions say "...Ignition timing should be set 2degrees retarded on the leading and trailing."
There is nothing about disconnecting the vacuum lines or locking the dizzy.
I just want to make it clear this is a DRAWTHROUGH setup... the carb will ALWAYS have vacuum, even when i'm running 17psi boost (just before the engine blows.. lol.. I will NOT be boosting that much).
Most of the AWESOME advice people are giving me seems to be coming from peeps with BLOWTHROUGH setups. LOL, just wants to make that clear.
There is nothing about disconnecting the vacuum lines or locking the dizzy.
I just want to make it clear this is a DRAWTHROUGH setup... the carb will ALWAYS have vacuum, even when i'm running 17psi boost (just before the engine blows.. lol.. I will NOT be boosting that much).
Most of the AWESOME advice people are giving me seems to be coming from peeps with BLOWTHROUGH setups. LOL, just wants to make that clear.
02-02-09, 05:27 AM
#53
And nope I don't own a turbo rotary at the moment. What of it? Doesn't make U any smarter. I have owned boosted rotary's and worked/helped out on many.
Not my fault U don't know how to tune your car properly. I'm just trying to help. If you don't like it.... stop posting.
02-02-09, 07:55 AM
#54
Think about it a minute. The timing curves on NA rotaries aren't much different than any other NA piston engine or otherwise. They are all just big pumps. Don't car if your pushing air with rotors or pistons. So why do think locking timing at some magic 10* is going to net best performance?
The more timing U can throw at them without detonation the better. Rotaries aren't *special*. They will react just like any other engine. As much as I know some of U rotards would like to think the rotary is some crazy space age technology that only a select few are aware of….it’s not.
And to say U can’t run as much timing on on a draw though setup? Care to explain? I don’t see why you couldn’t? How does a draw though VS a blow through affect timing?
There are only 3 major only limiting factors of a draw through I am aware of.
First is the fuel has to pass through the compressor of the turbo. So you will begin to have efficiency issues once your trying to run a ton of fuel through turbo. So if you have the meth injection down stream of the turbo you’ll be able to run more boost. IMO 10psi+ easy on that tiny turbo. @15* timing would work nicely.
Also the fuel will wear the comp. wheel over time at higher fuel loads.
Lastly….and most importantly. You will need a carbon seal turbo. The one you selected will not work properly.
There are two different types of seals in turbochargers: dynamic (aka piston) and carbon (aka positive). The carbon seal is suitable for either blow-through or draw-through applications. Dynamic seals are suitable for blow-through only! I repeat, you cannot use a dynamic seal on a draw-through turbo system. This is important. Ideally, you would select a turbocharger that came with a carbon seal already in it, and save youself a lot of headaches later. Unfortunately, carbon seal turbos are a rarity, because the newer dynamic seal is more efficient, and well suitable to the fuel injected engines that are used these days. So, the moral of the story is if you want a draw-through setup, either a) find a turbo with a carbon seal, or b) rebuild your turbo and convert it to carbon seal.
A dynamic seal uses a couple of piston rings, much like the rings on the pistons in your engine. As you should know, a piston ring isn't a 100% seal. There's a little gap in the ring. For a blow-through turbocharger, this is fine. The compressor will always be pressurized, and no oil will get sucked through that little ring gap.
However, when you have a draw-through setup, the carb is mounted on the intake side of the compressor. Thus, any time the throttle is closed, there will be manifold vacuum inside the compressor housing. Think about it -- most of the time when you're not accellerating, there is manifold vacuum. If you have a dynamic seal with the little piston rings, then this manifold vacuum will suck the oil out through that little piston ring gap. It'll suck the oil right into your motor, and you're engine will run like some idiot put 2-cycle mix in the gas tank. This is bad. You'll foul your plugs and upset your neighbors. The oil will reduce your octane, and you might even get detonation.
The carbon-seal, on the other hand, has a spring-loaded ring that presses against a thrust collar on the turbine shaft. There is no "gap" in the carbon seal; it seals all the way around. It'll keep that oil in there, even in the presence of manifold vacuum in the compressor housing.
So, this is where the project will start to get expensive.
$150 for a turbocharger rebuild kit. $40 for a carbon seal. Then you will notice that the carbon seal needs a special "thrust collar" that isn't part of the regular rebuild kit. So another $30 + shipping for a thrust collar. A cheap $50 turbo will end up costing upwards of $300 after all of the rebuilding is complete. And that’s if you do the work yourself!
My suggestion if you are going to keep this setup is to find an olderstyle draw through turbo and have it rebuilt.
The more timing U can throw at them without detonation the better. Rotaries aren't *special*. They will react just like any other engine. As much as I know some of U rotards would like to think the rotary is some crazy space age technology that only a select few are aware of….it’s not.
And to say U can’t run as much timing on on a draw though setup? Care to explain? I don’t see why you couldn’t? How does a draw though VS a blow through affect timing?
There are only 3 major only limiting factors of a draw through I am aware of.
First is the fuel has to pass through the compressor of the turbo. So you will begin to have efficiency issues once your trying to run a ton of fuel through turbo. So if you have the meth injection down stream of the turbo you’ll be able to run more boost. IMO 10psi+ easy on that tiny turbo. @15* timing would work nicely.
Also the fuel will wear the comp. wheel over time at higher fuel loads.
Lastly….and most importantly. You will need a carbon seal turbo. The one you selected will not work properly.
There are two different types of seals in turbochargers: dynamic (aka piston) and carbon (aka positive). The carbon seal is suitable for either blow-through or draw-through applications. Dynamic seals are suitable for blow-through only! I repeat, you cannot use a dynamic seal on a draw-through turbo system. This is important. Ideally, you would select a turbocharger that came with a carbon seal already in it, and save youself a lot of headaches later. Unfortunately, carbon seal turbos are a rarity, because the newer dynamic seal is more efficient, and well suitable to the fuel injected engines that are used these days. So, the moral of the story is if you want a draw-through setup, either a) find a turbo with a carbon seal, or b) rebuild your turbo and convert it to carbon seal.
A dynamic seal uses a couple of piston rings, much like the rings on the pistons in your engine. As you should know, a piston ring isn't a 100% seal. There's a little gap in the ring. For a blow-through turbocharger, this is fine. The compressor will always be pressurized, and no oil will get sucked through that little ring gap.
However, when you have a draw-through setup, the carb is mounted on the intake side of the compressor. Thus, any time the throttle is closed, there will be manifold vacuum inside the compressor housing. Think about it -- most of the time when you're not accellerating, there is manifold vacuum. If you have a dynamic seal with the little piston rings, then this manifold vacuum will suck the oil out through that little piston ring gap. It'll suck the oil right into your motor, and you're engine will run like some idiot put 2-cycle mix in the gas tank. This is bad. You'll foul your plugs and upset your neighbors. The oil will reduce your octane, and you might even get detonation.
The carbon-seal, on the other hand, has a spring-loaded ring that presses against a thrust collar on the turbine shaft. There is no "gap" in the carbon seal; it seals all the way around. It'll keep that oil in there, even in the presence of manifold vacuum in the compressor housing.
So, this is where the project will start to get expensive.
$150 for a turbocharger rebuild kit. $40 for a carbon seal. Then you will notice that the carbon seal needs a special "thrust collar" that isn't part of the regular rebuild kit. So another $30 + shipping for a thrust collar. A cheap $50 turbo will end up costing upwards of $300 after all of the rebuilding is complete. And that’s if you do the work yourself!
My suggestion if you are going to keep this setup is to find an olderstyle draw through turbo and have it rebuilt.
02-02-09, 02:30 PM
#55
Everything in your last post is correct. 10* is not the best performance, but the safest. Most guys get the best around 15-17*, but that's on intercoolded EFI cars. Being drawthrough he has one huge disadvantage, heat heat heat. drawthrough cars run hotter than blowthrough or EFI turbo so you can't run as much timing due to the heat and the ease of detonation.
02-02-09, 02:58 PM
#56
Everything in your last post is correct. 10* is not the best performance, but the safest. Most guys get the best around 15-17*, but that's on intercoolded EFI cars. Being drawthrough he has one huge disadvantage, heat heat heat. drawthrough cars run hotter than blowthrough or EFI turbo so you can't run as much timing due to the heat and the ease of detonation.
Why are you saying a draw through runs hotter? Maybe I'm missing something? Is it just because of the lack of an IC?
I'd say a non-intercoolerd draw through would run just as cool as a non-IC blow through. And if you add the chemical intercooling on top of that (meth injection). It will help tremendously.
I don't have non intercooled draw through exp. on a rotary. But I have worked with alot of non intercooled, chemical cooled turbo engines. And IMO methanol works better than a standard air to air FMIC.
I choose to run both on all my cars. But in his case, I still say he could lock timing at 15* and run 10psi all day on 91 octane. (assuming he had the correct turbo/proper tune).
02-02-09, 03:18 PM
#57
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Didn't mean to be a dusche in the last post. I'm a big boy, and can admit when I'm wrong. Although I still don't see any information proving me wrong.
Why are you saying a draw through runs hotter? Maybe I'm missing something? Is it just because of the lack of an IC?
I'd say a non-intercoolerd draw through would run just as cool as a non-IC blow through. And if you add the chemical intercooling on top of that (meth injection). It will help tremendously.
I don't have non intercooled draw through exp. on a rotary. But I have worked with alot of non intercooled, chemical cooled turbo engines. And IMO methanol works better than a standard air to air FMIC.
I choose to run both on all my cars. But in his case, I still say he could lock timing at 15* and run 10psi all day on 91 octane. (assuming he had the correct turbo/proper tune).
Why are you saying a draw through runs hotter? Maybe I'm missing something? Is it just because of the lack of an IC?
I'd say a non-intercoolerd draw through would run just as cool as a non-IC blow through. And if you add the chemical intercooling on top of that (meth injection). It will help tremendously.
I don't have non intercooled draw through exp. on a rotary. But I have worked with alot of non intercooled, chemical cooled turbo engines. And IMO methanol works better than a standard air to air FMIC.
I choose to run both on all my cars. But in his case, I still say he could lock timing at 15* and run 10psi all day on 91 octane. (assuming he had the correct turbo/proper tune).
please refrane from giving any more advice as you have no expierience with a draw through system or how it works. thanks
02-02-09, 03:20 PM
#58
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Everything in your last post is correct. 10* is not the best performance, but the safest. Most guys get the best around 15-17*, but that's on intercoolded EFI cars. Being drawthrough he has one huge disadvantage, heat heat heat. drawthrough cars run hotter than blowthrough or EFI turbo so you can't run as much timing due to the heat and the ease of detonation.
02-02-09, 03:25 PM
#59
I know plenty about draw through setups. If you weren't a moron you'd be able to use some common sense and relate the two. If you've worked on one, they are all very similar. I'd say it's a safe bet I know alot more than you do. I'm the only one that gave any real information. I just said I never worked a blow through on a rotary before. Although I have worked on plenty of rotaries.
So if you'd like to prove me wrong in anyway I welcome it.... Please enlighten me oh wise one.
Unless U can bring something worth while to the conversation, I'd ask U to REFRAIN (look I can spell it right too!) from posting anymore on the subject.
02-02-09, 04:20 PM
#60
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nuff said!
even with meth injection you wouldnt want to run more than 12 psi with minimal advance to insure a reliable setup. on a turbo ROTARY application you dont need to run aggressive timing to make good power. with 8-10 psi on a boosted rotary with a locked distributor you will easily make close to 300 hp wich is pleanty power for the street.
generally unless your running race gas or E85 you dont want to boost more than 15-18 psi on an intercooled efi setup so on a non intercooled heat pump draw through system 10 psi with a locked distributor is max for reliability.
02-02-09, 04:56 PM
#61
nuff said!
even with meth injection you wouldnt want to run more than 12 psi with minimal advance to insure a reliable setup. on a turbo ROTARY application you dont need to run aggressive timing to make good power. with 8-10 psi on a boosted rotary with a locked distributor you will easily make close to 300 hp wich is pleanty power for the street.
generally unless your running race gas or E85 you dont want to boost more than 15-18 psi on an intercooled efi setup so on a non intercooled heat pump draw through system 10 psi with a locked distributor is max for reliability.
even with meth injection you wouldnt want to run more than 12 psi with minimal advance to insure a reliable setup. on a turbo ROTARY application you dont need to run aggressive timing to make good power. with 8-10 psi on a boosted rotary with a locked distributor you will easily make close to 300 hp wich is pleanty power for the street.
generally unless your running race gas or E85 you dont want to boost more than 15-18 psi on an intercooled efi setup so on a non intercooled heat pump draw through system 10 psi with a locked distributor is max for reliability.
I suggested 15* and 10psi with meth inj. and a proper tune. And I stand by that. Running 10* is a waste. It will put more heat in your exhaust and you will lose power. So why do it? Guys did that a long time ago before they had WB02's for proper tuning. That's old school tuning. It's out dated and just plain ignorant thinking with all the new technology.
Please someone with a brain chime in here and get these little half-wits off my heels!
02-02-09, 05:01 PM
#63
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I sure wish you slow guys would take a little longer to R E A D what was I said before opening your mouths. Maybe take the time to comprehend a little? Like I said spaz.... I never told him to run 25* timing or 25psi. That is what I run. And I've run as much as 29* timing and 30psi on 91 and meth injection without issues or detonation. But that's not the point....
I suggested 15* and 10psi with meth inj. and a proper tune. And I stand by that. Running 10* is a waste. It will put more heat in your exhaust and you will lose power. So why do it?
I suggested 15* and 10psi with meth inj. and a proper tune. And I stand by that. Running 10* is a waste. It will put more heat in your exhaust and you will lose power. So why do it?
and secondly 10 degrees advance is reccomended for SAFETY- get it spaz!!!!!
my mechanic made over 700 hp on his 12a turbo and his timing was locked at 10 degrees advanced. you dont need tons of timing on a rotary to make good power!it was also on 118 octane race gas..
02-02-09, 05:13 PM
#64
you sure dont run that much timing and boost on a rotary, i dont care if you have meth injection, your ROTARY WILL BLOW UP!!!!!
and secondly 10 degrees advance is reccomended for SAFETY- get it spaz!!!!!
my mechanic made over 700 hp on his 12a turbo and his timing was locked at 10 degrees advanced. you dont need tons of timing on a rotary to make good power!it was also on 118 octane race gas..
and secondly 10 degrees advance is reccomended for SAFETY- get it spaz!!!!!
my mechanic made over 700 hp on his 12a turbo and his timing was locked at 10 degrees advanced. you dont need tons of timing on a rotary to make good power!it was also on 118 octane race gas..
As boost goes up timing goes down. Larger the turbo the less timing is needed as well. Once again common sense. Difference between U an I is I am a mechanic...Ur just someone who watches on the side as others do the work for you.
15* is plenty safe for low boost. but like I said that turbo won't work without the proper seals!
02-02-09, 05:24 PM
#66
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a t25 turbo is small for a rotary, the hot side is very restrictive for a rotary. increased back pressure on a rotary=more heat internally= detontnation. this is why i reccomended 10 degrees. the hot side will choke the life out of a rotary. ell a stock turbo 2 torbo is a 1.0 hotside and the turbine wheel isnt much smaller than a p trim.. thats huge compared to a t25!
also ANY turbo for a draw through setup must be modified to not leak gas into the turbo center section as well as out of the turo itself.. ths includes installing a carbon seal and using an o-ring on the compressor cover. keep in mind, this is a limited procedure than only some turbo shops are capable of doing on certain types of turbos.
also ANY turbo for a draw through setup must be modified to not leak gas into the turbo center section as well as out of the turo itself.. ths includes installing a carbon seal and using an o-ring on the compressor cover. keep in mind, this is a limited procedure than only some turbo shops are capable of doing on certain types of turbos.
02-02-09, 05:26 PM
#67
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you can stack the leading and trailing timing but with a 5 degree split you will make more power and better driveability too
02-02-09, 05:34 PM
#68
Only good production vehicle I can think of that ran those were the ISUZU MPR Trucks back in the 80's. They were IHI RHB6-A's though. Does it have an A after it? That should have a pretty big rear housing.... Got any numbers stamped on it?
If it's not an a it's junk... and has a tiny housing. Probably off a Mazda 626 '83-'83, Mazda MX6 (1st gen) or a Fiat Spyder '81-'82
02-02-09, 07:08 PM
#70
Didn't mean to be a dusche in the last post. I'm a big boy, and can admit when I'm wrong. Although I still don't see any information proving me wrong.
Why are you saying a draw through runs hotter? Maybe I'm missing something? Is it just because of the lack of an IC?
I'd say a non-intercoolerd draw through would run just as cool as a non-IC blow through. And if you add the chemical intercooling on top of that (meth injection). It will help tremendously.
I don't have non intercooled draw through exp. on a rotary. But I have worked with alot of non intercooled, chemical cooled turbo engines. And IMO methanol works better than a standard air to air FMIC.
I choose to run both on all my cars. But in his case, I still say he could lock timing at 15* and run 10psi all day on 91 octane. (assuming he had the correct turbo/proper tune).
Why are you saying a draw through runs hotter? Maybe I'm missing something? Is it just because of the lack of an IC?
I'd say a non-intercoolerd draw through would run just as cool as a non-IC blow through. And if you add the chemical intercooling on top of that (meth injection). It will help tremendously.
I don't have non intercooled draw through exp. on a rotary. But I have worked with alot of non intercooled, chemical cooled turbo engines. And IMO methanol works better than a standard air to air FMIC.
I choose to run both on all my cars. But in his case, I still say he could lock timing at 15* and run 10psi all day on 91 octane. (assuming he had the correct turbo/proper tune).
you can run no split, but you'll get better gas mileage, better driveability, and klill less bunnies with a 5-8* split.
02-02-09, 08:17 PM
#71
update .. Monday 2/2/09
UGH.. I may have overestimated how quickly I could get this done.. LOL
So far the I've installed the exhaust manifold, vacuum side and pressure side intake manifolds and the turbo itself, oil feed line and oil return line, fabbed up downpipe and I put the carb on.
I had to make up a throttle cable bracket to fit new carb configuration. Dropping/re-installing the oil pan to install an oil return line turned out to be a much longer ordeal than I had antisipated. It's official, a 12a oil pan = the anti-christ. At least when working on it while still in the car.. ugh
Tonight or maybe tomorrow I will connect the downpipe to the rest of my exhaust, install my wideband, install my boost gauge and plump up my carb.... Than *cross fingers* start her up. Once I've got it running I will lock the dizzy (set leading to 10* and trailing to TDC-2* advance with vacuum pots disconnected), swap in my new fuel pump and filter.
Soooo... getting closer. Would help if I wasn't sick with a sinuous infection, but, sometimes that's how the dice lay.
So far the I've installed the exhaust manifold, vacuum side and pressure side intake manifolds and the turbo itself, oil feed line and oil return line, fabbed up downpipe and I put the carb on.
I had to make up a throttle cable bracket to fit new carb configuration. Dropping/re-installing the oil pan to install an oil return line turned out to be a much longer ordeal than I had antisipated. It's official, a 12a oil pan = the anti-christ. At least when working on it while still in the car.. ugh
Tonight or maybe tomorrow I will connect the downpipe to the rest of my exhaust, install my wideband, install my boost gauge and plump up my carb.... Than *cross fingers* start her up. Once I've got it running I will lock the dizzy (set leading to 10* and trailing to TDC-2* advance with vacuum pots disconnected), swap in my new fuel pump and filter.
Soooo... getting closer. Would help if I wasn't sick with a sinuous infection, but, sometimes that's how the dice lay.
02-02-09, 08:55 PM
#72
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If you're not running alcohol (either as the main fuel or auxiliary injection), there doesn't seem to be much to be gained from aggressive split. I'd rather set my split to 10 degrees or so and advance leading a little instead, as leading timing has a much greater effect on power.
02-02-09, 10:43 PM
#74
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I'm running 9 PSI. Leading timing is 5 degrees ATDC at 1000 RPM idle, 10 degree split, no vacuum advance. I believe that equates to a little under 15 degrees BTDC at full mechanical advance. Remember also that I have 9.2:1 rotors.
02-03-09, 07:24 AM
#75
non intercooled blowthrough will run coolder from the chemicle intercooling effect of the gas atomizing in the carb. in a drawthrough setup ambiant air is cooled when it goes through the carb then it's reheated in the compressor housing. With blow through ambiant air is heated in the compression housing them cooled as it goes through the carb.
you can run no split, but you'll get better gas mileage, better driveability, and klill less bunnies with a 5-8* split.
you can run no split, but you'll get better gas mileage, better driveability, and klill less bunnies with a 5-8* split.
But lets suppose your right for a minute......
With chemical intercooling I still say it's water (meth?) under the bridge.
If it were my setup I'd also run a very small 1gpm nozzle in front of the compressor. And a 5-10gpm after the tubo. Depending on how much boost/timing I was wanting to run.
Compression in a turbo is adiabatic as you said. This means that the air is heated as it is compressed, which takes power from the shaft and is usually counter balanced through the use of an intercooler.
But....
If you inject water/meth before the turbo, then you can move compression to near isothermal, so very little heat is added, and less power is taken from the turbine to compress the air for the same boost level. You can remove the intercooler and therefore suffer less pressure drop between compressor and inlet. All of which gives you the possibility to get more power out the same turbo. Not to mention the added octane and anti-detonation characteristics of the meth.
As far as timing goes.
I’d tend to agree that on paper running a split sounds great. And NA running split timing does work better (Yaws claims 12A’s work best with an 8* split BTW).
But through my experience when you add boost to the equation this usually causes problems. Maybe this is why you all don’t run higher base timing? With a trailing plug firing under the accelerated heats of a boosted engine detonation is more likely to occur. The holley knock sensor we were running sure didn’t like the 10* base timing and 10* split we were running on my friends 13b-T.. But if we sync’d L and T ign. And ran 15-18* base timing and the knock sensor never detected any knock.