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DRAG Engine Build Specifically for 68hta..

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90laserRSfwd

15+ Year Contributor
1,412
84
Mar 5, 2007
Elizabethtown, Pennsylvania
I'd like to start an open discussion, with focus SPECIFICALLY on building a long block (block and head), to utilize the full capabilities of Forced Performances 68hta. It's obvious that the only way to utilize the full potential of the 68hta is going to be excluding the use of pump gas. Ethanol (60% - 98%), Methanol (M1 more then likely), or the higher end of VP, Torco, or Sunoco, etc's racing fuels are going to be the only options.

Keeping the fuel choice in mind, I ASSume, that any compression ratio less then 9:1, wouldn't be utilized.

I'd like to know what everyone else thinks would be the IDEAL build specifically for maxing out the 68hta.
 
I'd like to start an open discussion, with focus SPECIFICALLY on building a long block (block and head), to utilize the full capabilities of Forced Performances 68hta. It's obvious that the only way to utilize the full potential of the 68hta is going to be excluding the use of pump gas. Ethanol (60% - 98%), Methanol (M1 more then likely), or the higher end of VP, Torco, or Sunoco, etc's racing fuels are going to be the only options.

Keeping the fuel choice in mind, I ASSume, that any compression ratio less then 9:1, wouldn't be utilized.

I'd like to know what everyone else thinks would be the IDEAL build specifically for maxing out the 68hta.
Well for starters are you planning this for street only or is this a track only car? Are you planning on getting to a certain horsepower number? These decisions would change a lot of what direction we would tell you to go.

You are correct about the compression ratio. If you plan on only running everything but pump gas then you'll want to have a higher compression ratio. I'm currently building a new engine that is never going to run pump gas either and I'm getting custom 11.5:1 compression ratio pistons.

Although that turbo can do very well with all different types of fuels. If you want to realize the best potential with pump gas you'll need to get meth injection and you can stick with 9:1 but it the tune would be crucial. If you have easy access to e85 then I would use that but that depends on what you have near you. If this is a dedicated track car then pump gas would be irrelevant and just build the engine for what fuel you have available at the track.

Truthfully with that turbo you'll want to make a torque monster like a 2.3l or 2.4l. The hta68 will have limitations in the high RPM's and will spool almost immediately so a stroker would be the best option.
 
@Vegas: Building a motor that your trying to get the most power out of with the limiting factor being air flow, pump gas (and there for low static compression ratio's) are not even a choice.

@kamikazeredneck This discussion is based on producing the most power that can be made. Although I agree building a motor around each motorsport base would be slightly different (drag racing, road course, etc), but for arguments sake, lets just say drag use.

My choice would be a 2.0 build with 10:1 compression utilizing a 2g head with long duration cams. Being that the new 68hta has a larger turbine wheel, I don't feel the need to shift before 7K rpm any longer. I feel a 2.0 build would out shine a 2.3 build in a drag build. The issue with building a torque monster, is the same reason people avoid high RPM motors, the transmissions DO NOT LIVE. I feel running the motor to 7,800 - 8,000 RPM is the best answer. We've all read time and time again that strokers and high rev's are a bad match. If this was a street car, a stroker would be a better choice perhaps, but since it's set to be a drag motor, it's not going to see much low end use, at all..
 
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@Vegas: Building a motor that your trying to get the most power out of with the limiting factor being air flow, pump gas (and there for low static compression ratio's) are not even a choice.

@kamikazeredneck This discussion is based on producing the most power that can be made. Although I agree building a motor around each motorsport base would be slightly different (drag racing, road course, etc), but for arguments sake, lets just say drag use.

My choice would be a 2.0 build with 10:1 compression utilizing a 2g head with long duration cams. Being that the new 68hta has a larger turbine wheel, I don't feel the need to shift before 7K rpm any longer. I feel a 2.0 build would out shine a 2.3 build in a drag build. The issue with building a torque monster, is the same reason people avoid high RPM motors, the transmissions DO NOT LIVE. I feel running the motor to 7,800 - 8,000 RPM is the best answer. We've all read time and time again that strokers and high rev's are a bad match. If this was a street car, a stroker would be a better choice perhaps, but since it's set to be a drag motor, it's not going to see much low end use, at all..
If you want to keep the 2.0l then I would build one with 11:1 compression with a built head. If you want 8000rpms+ then you'll need something like a 272cam and maybe 1mm oversized valves. You'll also have to upgrade the springs to handle the cams and rpms. It's quite an easy build but I don't know how much top end you'd get with that turbo. That specific turbo is much more suited for people that want a great street car or maybe something that spools quickly for autocross or road racing. That's just my 2 cents but good luck with the build!
 
I think everyone is expecting to build a motor to support this turbo (51 lbs / min according to FP). I'm curious as to your reasoning for 11:1 compression ratio and or using a 2.3 stroker or 2.4L. I understand, that if this was intended to be a street car that see's track use, that a stroker (or 2.4L) would make sense. Just curious that's all. Maybe I'll learn something new.
 
I think everyone is expecting to build a motor to support this turbo (51 lbs / min according to FP). I'm curious as to your reasoning for 11:1 compression ratio and or using a 2.3 stroker or 2.4L. I understand, that if this was intended to be a street car that see's track use, that a stroker (or 2.4L) would make sense. Just curious that's all. Maybe I'll learn something new.
I have an old 50trim right now and am seeing about 50lbs at 7500ft so I have around the same system.

The reason I would say that you should do 11:1 is because of your fuel choice. When you use something like e85 or anything other than pump gas really, you'll want to up the compression to get a much better and more complete burn. If you had pump gas you'd be more likely to see knock but with the fuels you are looking into you'll be able to up the compression quite a bit. I know that some people with meth or alcohol engines run as high as 12.5:1 with a turbo because of this reason.

I was saying a stroker build was because with that turbo it would probably max out around 8000rpms (at least that's what I've seen with mine) and with a stroker you'd only rev it to around 7500 or 8000rpms anyway and it would work with that turbo so much better as that's where that turbo's efficiency would be. With a 2.0 you can rev 8000rpms easy with a stock top end and anything more than 8000rpms that turbo won't be any use (once again from my experience with a similar turbo).

To be completely honest though that turbo isn't going to be that great for a drag car. That turbo is perfect for street, autocross or road racing. With a drag build you want top end so the bigger the turbo the better.
 
I see your point. The only reason I suggested staying away from the 2.3 or 2.4 build is because everyone knows torque kills these transmissions. Also, with a turbo this small, there really is no reason to use a 2.3 or 2.4 to help spool (or shift the power band to the left). The only benefit would be the power coming in sooner, which isn't an issue (from what I've gathered), or possibly producing more torque. I have a friend with an 11:1 compression 2.4L in his EVO, and it's great for the street. His car is on e85 (closer to 70% ethanol more then likely), and the car drives like a stock 2.0L with a stock turbo. Torque is great and boost comes in early (his car has a 35r on it). For a street car, a stroker (or 2.4L) may be ideal, but a drag car is going to be under full throttle, low RPM, ONLY when not being raced. Also, with this motor we are discussing, ONLY being used for a drag application, engine wear is an obvious concern. I feel adding the additional piston side load force and related rod bearing stress of a (horrible rod angle'd 2.3L stroker), being worth the extra wear it would cause. I understand the 2.4L wouldn't have the same issue, but finding a 2.4 6 bolt block is no easy task these days. There is a 2.4L long rod option, but we don't need a 10K RPM capable motor...

Overall I think a simple 2.0L build with upped compression (10:1 like I suggested, or 11:1 like you suggested), is all that is needed in this particular case :)
 
I see your point. The only reason I suggested staying away from the 2.3 or 2.4 build is because everyone knows torque kills these transmissions. Also, with a turbo this small, there really is no reason to use a 2.3 or 2.4 to help spool (or shift the power band to the left). The only benefit would be the power coming in sooner, which isn't an issue (from what I've gathered), or possibly producing more torque. I have a friend with an 11:1 compression 2.4L in his EVO, and it's great for the street. His car is on e85 (closer to 70% ethanol more then likely), and the car drives like a stock 2.0L with a stock turbo. Torque is great and boost comes in early (his car has a 35r on it). For a street car, a stroker (or 2.4L) may be ideal, but a drag car is going to be under full throttle, low RPM, ONLY when not being raced. Also, with this motor we are discussing, ONLY being used for a drag application, engine wear is an obvious concern. I feel adding the additional piston side load force and related rod bearing stress of a (horrible rod angle'd 2.3L stroker), being worth the extra wear it would cause. I understand the 2.4L wouldn't have the same issue, but finding a 2.4 6 bolt block is no easy task these days. There is a 2.4L long rod option, but we don't need a 10K RPM capable motor...

Overall I think a simple 2.0L build with upped compression (10:1 like I suggested, or 11:1 like you suggested), is all that is needed in this particular case :)
A 2.0l will do the job for sure, I was just suggesting things based on your post which was how to maximize efficiency of the turbo and engine combo. I personally think that a 2.0 won't give you the best setup as the 2.0 likes to rev and that turbo won't get the flow up top. If you are worried about the torque from a 2.3l or 2.4l then I would say use an electronic boost controller with gear based boost control in ECMLink or other ECU boost control. I agree with you on the torque being a possible problem with a stroker and I am going to be running into the same issue when I get around to putting my new engine in my car. I'm going to use gear based boost control in link to solve this problem and keep my tranny alive as long as possible as I will be seeing a ton of torque on the low end from the compression and turbo.

Ultimately it's up to you and either way you go I don't think you'll be unhappy but I think that you'll loose a lot up top with that turbo at any revs above 7000. Good luck with the build and hopefully you can find a sweet spot
 
I'm not sure I'm understanding your logic. You wouldn't want to reduce boost at all. Instead you'd reduce total torque by reducing timing. There is no reason to run the turbo at a lower boost level unless you are monitoring back pressure and need to reduced boost because you've exhausted other options of reducing back pressure. The other option would be that the boost level you are operating the turbocharger at is over-spinning the turbo. I still am not following your proposal that using a stroker is going to be a better setup for a drag only car then a 2.0. I'm not trying to sound disrespectful in any way, but when you say "I think that you'll lose a lot up top with that turbo at any revs about 7000", are you implying that a stroker motor will still make power above 7K and a 2L will not? If anything the power would fall off even sooner with a larger displacement motor then with a smaller one. Maybe I'm over thinking things, but I still feel like the 2L is a better choice then any other option, money or time wise.
 
After PMing a few guys on here about some idea's (nothing out of the norm), I decided to give this a shot. A lot of these threads turn into, for the lack of a better term, bench racing. I'll throw a couple pic's of shortly. Pulled the motor out of my 90 to use as a test mule. I have a gen2 68hta (I call it a gen2 because it used the bigger non MHI turbine wheel and 8cm2 housing instead of the 7cm2 and td05h wheel the gen1's came with). My engine is a bone stock 6 bolt. Car currently has 98K miles on it.
 
My intentions are to refresh the stock motor, and get a few passes on both pump gas and e85 (only about 70% ethanol at my local pump). To get a good baseline on a stock (refreshed) motor.

I'm going to pick up (a second) 6 bolt block and head to build a high(er) compression motor (10:1 or 11:1 range) and put a set of springs/retainers/mild cams in the head and see what difference the build motor makes. I'll post up some pic's when I get the engine core and other parts in. Feel free to chime in with your thoughts/idea's!

I currently have a set of genuine HKS 264/272 cam combo sitting here, but I'm not sure if I wanna put it in the stock motor, because we all know cams make a pretty decent change to VE.
 
I'm surprised after all the hype of the 68hta, there's not more responses here..

At the end of the day, it's still as expensive as the larger options, so unless you're specifically shooting for a stock appearing setup or want the most power possible with insta-spool, most people just go bigger.
 
Maybe aluminum rods and balance cranks? Ported and polished head.........Depending on the compression used maybe nitrous. Put in some methonal with "high lift/ medium duration cams" and let it eat................ With small turbos, it's all about the little stuff to get a good number.
 
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