Which Cylinder head?
 

Just to warn you I love talking about engine dynamics, so please if you are going to suggest one, back it up with a reason. I know this has been talked to death but I don't think I found an answer to this question.

I am figuring out which head should I go with, the 1g or the 2g. Reading DSM tuners and vfaq, I am confused on what I should do. 1g has bigger intake ports. However there hasn't been any test done to see if that actually helps HP. It is just an assumption by people just comparing the intake ports. There are a lot of people throwing 1g heads on 2g engine blocks. There maybe some proof but it could be false proof by the difference in cams between the 1g and the 2g. However there has to be a reason why the stock 2g cars (215 hp) are making more hp and tq then the stock 1g (190hp).
The 2g head has a better angle for the air to enter onto the intake valve, which I heard is better then having the bigger intake. This has been sort of proven with the evos still having the same intake size as the 2g. And they are making good horse power yet. The 2g is also built with better metal then the 1g. My guess is the 1g does better in the higher RPM. However this car is only going to see the max RPM of 7500 so is that really considered high rpm on this car or does that mean going past redline...

what do you think I should do? I value any opinion I get.

The other question is how much will this actually matter. Will I even see much of a difference? When people run their cars on the dyno, it seems like they only look at max rpm but I am going to be looking to see what I am making in the lower rpm as well in the higher rpms.

I should probably mention what I have planned for the car so that better advice can be given. I am not building a High HP car. I am looking for good responce from the engine and the turbo from across the rpm range, not just the high rpm

I am going to go with the 1g rods with 2g pistons so I can have a compression of 8.5

I am building a MegaSquirt system to play around with (I am a DIY type person so I enjoy any chance of building stuff) The MS system is going to take over the stock ECU. I will have full tuning capabilities, also a wide band will be purchased for tuning. Going to go with MAP

255hp with a Aeromotive FPR (bigger injectors are going to be purchased soon, I don't know how big)

FMIC with hard pipes

3" exhaust system w/o cat

built my own boost controler

ACT 2600 clutch

Leaving the transmission stock (was rebuilt 10,000 miles ago)

Evo 3 exhaust manifold

Haven't figured out what turbo yet...

I want to go to E85 for the 108 octane so I won't be dealing with knock but still a little confused on what I need to do to the car to make it compatible. Where should I go to get the fuel rail treated?

Anything else I am forgetting

Spring is comming and I want to get the DSM out very soon!!!

Re: Which Cylinder head?
 

Your HP goals are really going to make a big difference on which head you go with. It sounds like a 2g head is going to work better for you. I would put some 272's on your list too. The reason the 2g's have more HP stock is that they run more boost stock. A 1g at the same psi makes more HP, mostly because of the 2g BOV and small T25.

I would also look at going with a Wiseco/Eagle combo. Higher compression is going to get you better spoolup and more torque. You could go with the 9.0:1 pistons and a thinner headgasket or custom order some 9.5:1 or so. How much HP are you planning on and which style of dyno?

Re: Which Cylinder head?
 

How much horse power... Isn't that the ultimate question....
Maybe I am kind of new to this but what do you mean by which style of dyno?

I am thinking if I got 350-450hp I will be very very happy. I kind of gave myself a limit on how much horsepower I want to give. Why, well it mainly has to do with money. I am broke! So I want to get the most out of my small budget. When I say 350-450 those are the top numbers. It is easy to get those numbers from just bolting up a turbo (well there is a little more to that then just a turbo bolt up...) but I am interested in making the engine perform well with the parts that I have added to give the car good responce. I am going to leave the transmission stock simply because it was rebuilt at the 10,000 miles ago and I don't have the money for a shep trans. I think (and hoping) that the stock trans will take the horse power. Passed the 500 hp limit, I know it won't. Plus I have to go buy a 4-bolt rear end for the car first before transmission. I also want to beef up the suspension which will be more money.

Definatly I should get the 272 cams

I went with the 8:5 compression just for better responce however I had a question about that. I have read somewhere that it does give better responce but it doesn't give better spool up time. The only reason people think so is because higher compression works better off boost before boost kicks in. Is this true and is there proof that the higher compression spools up turbos faster? I wasn't sure about this. I am more toward the idea that the only reason you get better responce is because 8:5 works better then 7:8 off boost and then when boost kicks in, you get more horse yet. And the the idea that 10 psi on a car with 7:8 compression is a lot different then 10psi on a car with 9:0 compression. I wanted to go with evo 3 pistons that had 9:0 compression but couldn't find any.

I am thinking the 2g head will work better also. I had the question then, would oversize valves help? or would that only be for higher RPM applications?

When I am out of college, I will have a much larger budget and I plan on building up an mitsu close to the 4 diget club. Then I will get the Wiseco/Eagle combo, shep transmission, and all the other good stuff that I have been dreaming about. But first I want to learn on my DSM first. I just want to play around with combos and see what works best. it is just the engine building I enjoy, and making the parts work well with eachother. Then taking information I believe I can build a kick ass Evo or something!:sasmokin:

And plus in the end which car would you have more respect for, a car that a kid just threw a lot of money in to make it run fast, or a car that someone put lots of time, custom diy parts, and actual practical engine building knowledge into the car.
I am getting sick of seeing cars that are built up and people still don't know why they are fast. All they know is if they buy this part it will give their car 20hp more. :angryfire:

Sorry got off subject a little. :rolleyes:

Re: Which Cylinder head?
 

I too looked into this about a year ago, and ended up deciding on the 2g head. Its smaller ports promote velocity and better cylinder filling at low and mid rpms, yet it doesnt seem to fall behind the large port 1g heads on the top end either.

Turbos are driven off of hot gas entering the turbine housing and expanding due to the drop in relative pressure. The turbine wheel captures this gas expansion as work.

A higher compression engine is going to have a higher pressure exhaust charge, which should facilitate earlier spool all things being equal.

Re: Which Cylinder head?
 

At 400 hp I am guessing it will be a toss up between which head to go with (on a DD dyno). The 2g is probably going to need some work at that point where the 1g still has more in it stock. Either one will work

Just start working your way up and see where you end up. I remember a time when all I wanted was 350 hp, it just keeps going up the more you get! I am to the point where I think I have enough though, it is pretty nutty on the street.

Re: Which Cylinder head?
 

I like this, it is back to the basics of engine building

I just have a question about this

"A higher compression engine is going to have a higher pressure exhaust charge, which should facilitate earlier spool all things being equal."

Does this mean that there is more exhaust given off on a higher compression engine which would give more spool to the turbo right? Then a higher compression engine would be burning the fuel at a more efficient rate (assuming that more exhaust means better fuel burn because of expantion) then a lower compression because the same amount of fuel would be entering both engine at the correct fuel ratio. Would this be safe to assume then that a compression of 8:5 would give me better MPG then 7:8 because 8:5 would be getting more power per fire?
I am guessing then it is only when the turbo spools up adding air pressure to the 7:8 it will even out. However the higher compression wouldn't need as much air pressure when the turbo kicks in and thats why it would take off the line faster.

O wow, it just clicked in my head


Wait then this puts the theory of JETs (sorry for picking on you) invalid.

"The reason the 2g's have more HP stock is that they run more boost stock. A 1g at the same psi makes more HP, mostly because of the 2g BOV and small T25."

How would the 1g make more horse power if both cars are running the same PSI. In theory the 2g should be making more HP because of the compression ratio.

This could go into turbo efficiency

if a 1g and a 2g were equal (exept for the compression) with the same turbo, 14b the 2g should be kicking the 1g butt. This could explain why the 14b is a popular upgrade for a 2g.

This then could go into octane ratings because fuel does have a point where it starts to detonate or knock. The highest octane would be 91-94 at the pump but if I switch over to E85 with higher compression that has a 108 octane I should be able to run more boost then running on the 91-94.

Re: Which Cylinder head?
 

Pertaining to the question "does a high compression engine generate more exhaust than a low compression version?" The short answer is no. The amount of exhaust given off is merely a function of volume (displacement). Mass going in and out of an engine is relatively constant, if you consider blowby to be minor (and it should be on a fresh engine).

As for the 1g and 2g power differences, the 14b can indeed flow far more air than the t25; its also more efficient at compressing air which simply means it heats the charge less.

E85 is actually 105 motor octane. Octane is merely a measure of how well a fuel can resist knock, so of course its going to have a higher threshold. Another benefit of that particular fuel is you can run a much more aggressive timing map.

Re: Which Cylinder head?
 

You are correct thinking the higher static compression only seems like the turbo is spooling faster. When you think about it, it only effects the compression stroke. Sure pressure builds up before the exhaust valve opens, but the difference would be minimal. I give it only 50 rpm better spool at beest.

Re: Which Cylinder head?
 

You need to be careful with this statement. The mass of air entering the intake manifold is not equal to the mass of gases leaving the exhaust manifold.

Re: Which Cylinder head?
 

Like I said the 2g makes less power for several reasons, mainly the BOV and smaller turbo. If everything else was equal the 2g head should be making more power, lower in the RPM range. When you start getting to higher HP levels you will have to start putting some money into the 2g head sooner.

Also, "the 2g should be kicking 1g butt", I don't think you will be seeing anything that drastic. You spend most of the time in the upper RPM range while racing so the difference would be minimal.

Re: Which Cylinder head?
 

I haven't heard of the fuel rail needing to be treated for E85. Anyone heard of it?

Re: Which Cylinder head?
 

Andrew, I suggest the 1G 7bolt head, as I understand it, it flows the best. And on turbo cars, flow is everything. I will go out to the garage and take some pics of both heads and post em later tonight.

The 2g head probably has better response when off boost, but comon, boost is life, go for alot of boost.

I agree with JET, I would go with forged internals, you wont regret it, the 1G rods are cast, and they can bend/break, and the 2g pistons are cast also, they can melt easier.

E85 - Let me answer this once and for all: you can run E85 in any car, all you need to do is re-program the ECU (or use an SAFC) People have been running E85 in cars for a long time with no problems, regular pump gas has 10% Ethanol, sometimes more.

I dont know why everybody assumes E85 will corrode the fuel system, it wont.

If I am incorrect on anything I said, feel free to correct me, lets keep the correct facts in circulation, not automotive superstition.

Re: Which Cylinder head?
 

Have you read any of the other posts in this thread regarding port size and air velocity?

Re: Which Cylinder head?
 

Yes, I have, but you have to find a happy medium between velocity and flow.

M.A.P. has a 500+awhp car, and they chose the 1g 7bolt head, because it "flows the best" I would put my money on the head with the biggest ports if I was using a huge turbo, if I had a t25/t28 the 2g head would probably work better.

Re: Which Cylinder head?
 

Then no you haven't been reading the previous threads....

I am not going for a huge turbo to make huge amounts of horse power. That is not the point of the thread. I already know that is possible to make huge horsepower with these engine with a huge turbo... I have realized that my car isn't going to be the fastest out there.

Also I have a 6 bolt motor with a 6 bolt head, why would I want a 7 bolt head? Did i forget to mention I had a 90 eclipse...wait i did sorry....

This will turn into my daily driver so I want to enjoy the car in all areas of the rpm range. Not just the top rpm or top hp range. I am sinking all of my money into another street project.

So it sounds like to me the 2g head will work better for me then the 1g so far....

Also You can take pictures of them as much as you want. I have seen pictures that compair both of the heads but I don't want to see size...
If you, look at both heads and see which one has better entry of air. What I have been told and have seen is that the 2g has better entry of intake. the 1g head has a horrible angle. I believe running more boost just covers up this problem in the long run.
Because of the angle of entry, the High HP cars I think are running the 2g head ported so that it flows better and in the long run will outflow the 1g .


"If I am incorrect on anything I said, feel free to correct me, lets keep the correct facts in circulation, not automotive superstition."

Thank you for posting this, this is my thoughts entirely, however if you are going to say this please back up your thoughts.

The idea that E85 "Won't" corrode your fuel system has to have backing. Why won't it? from what I understand, E85 is like Alcohol and it corrodes aluminum. Our fuel system is mostly aluminum and the head is aluminum. I thought you had to treat the fuel rail so that it doesn't corrode because fuel will constantly sit in it? Since my gas tank is metal (lucky 2g have plastic), won't I have to treat that? For the computer issue, I have that solved with a full stand alone system to control air and spark. :cool:

But if what you say is true, I have all the components to make the car run on E85? I don't need to do any more exept just fill it up and tune the computer (well I need bigger injectors ofcourse)? That would be sweet!

Ok back to the idea of generating exhaust gas, So did we determin that higher compression won't make the turbo spool faster and if so, it would be minimum and not noticable.
And if it did, the reason is that on the exhaust stroke it is pushing the exhaust out a touch faster because of the compression, not because of the amount of exhaust. This is more believable because if the 1g had lots of fuel unburned it would plug up the cat and there would be massive amount of backfires.

Ok I am going to talk NOT in racing terms but on highway crusing which is off boost. Would I be getting better MPG then because the car has higher compression and generating more power because of the compression.
For example on a lower compression, say going up hill with the cruise control set, the car would be forced to use more fuel in order to get more power from the 7:8. The 8:5 will use less fuel because it is gennerating more power per combustion. This I think would also be at an unnoticable level of fuel consumption, but fun to talk about.

Sorry about the "kick butt statement" I ment it would have the advantage. I don't want to make this sound like it will have a huge advantage. I know that it would be very minimum.

And the turbo differences between the T25 T28 is all on efficiency which is for another thread.

Re: Which Cylinder head?
 

Thanks for accusing me of not reading.

Listen, 350-450HP on the Dyno, ANY Dyno is huge engine HP. and you can use a 2g head, but you are going to have to make up for the restriction in the system somewhere else, bigger turbo/more boost.

The 1g 7-bolt head outflows/out performs the 1g 6-bolt head, its designed much better, everything bolts up fine, the only thing you will have to do is take it to a machine shop, or find someone with a drill press and have them drill out the head stud holes (BTW, you will have to do this with a 2g head also)(6-bolt=12mm/7-bolt=11mm(i think))

E85 will not damage your fuel system, everyone in minnesota runs E10(with the exception of some special stations), if what you feared about E85 where true, then E10 would also corrode the system, which it does not.....Still dont believe me? go to a gas station, fill up a large glass jar of E85, take an old fuel rail, put it in the jar, seal, wait and see. I did this test myself, and now I have a clean fuel rail, and one hell of a molotov cocktail to throw at all of the e85 haters out there!

Re: Which Cylinder head?
 

Dont build your motor with fuel economy in mind, there really is no point.

Build your motor to perform well for the HP that you want, I would go with the 8.5:1 pistons, 9 is a little steep for me.

if you want to have better fuel economy, you can order up a taller 5th gear for your car

http://www.teamrip.com/GENUINE_FACTORY_AWD_PARTS.html

(1/3rd way down the page)

10% taller 5th gear, they claim 27-30mpg, the cool part of it, is you can install it really easily, all the other gears are tough to take off.

Re: Which Cylinder head?
 

Well I struggled with which head to put on my 98 gsx. I knew the 1g has bigger ports but the 2 g has its benifits as well. In the end I decided to go with neither. I picked the evoIII head and Im porting it out. That way I have the best of both worlds. Shorter runners without sacrificing smaller ports. I also took i mind my own theory of similar parts should be kept together. The evoIII head and 2h head are the same except the evoIII has bigger cams and shorter runners.

Re: Which Cylinder head?
 

What are you talking about?

As long as the car is tuned it will have good gas mileage. Doesnt matter how much power it has, if its on pump gas, cruising down the highway, how is hurting the fuel economy?

I just delivered a car to a guy that has me install a roll cage and fix some other stuff on his car, the car ran 11.8 on 19psi and pump. I had to drive it 300 miles to deliver. The car used 10.4 gallons of gas. Tell me that car does not get good fuel economy because it has power.

As far as the head decision goes... I personally like the 2g head. The bowl, valve angles like you said, smaller ports and so forth. I gasket matched my intake ports to a 1g intake manifold which possibly hurt it but I am going for the most flow I can get. I dont think anyone as ever done the test, stock head for stock head to see the power difference. Would be interesting to see in my opinion.

Re: Which Cylinder head?
 

There was a test between heads. If I remember correctly, Polk Performance did it. Unfortunately I read it a long time ago on tuners and can't find it again. It's a little fuzzy from my head so take these numbers with a grain of salt. The 2g head only flowed 30 cfm less in stock form. However, the 1g head only flowed more 5500+rpm. Again, with a grain of salt.

My opinion, Andrew, is for you to go with the 2g head. That way, after you complete your goals; all you have to do is port the head and it will by far outflow any 1g head. Ported or not. That is, if you decide you should want more power after that.

As far as the E85 corrosion problem, you might as well get Viton O rings since you'll need a larger fuel pump and injectors anyway. It's up to you if you want to use the rubber fuel lines or not. I have used E85 but not enough to actually test the corrosiveness on rubber. I'd go with stainless braided lines anyway, it's a cleaner look and you get more fuel with the bigger lines. Also, this will aid when you install an adjustable fuel pressure regulator.

Re: Which Cylinder head?
 

My advice is no good, please delete.

Re: Which Cylinder head?
 

Holy novel! Dang swanny writes a friggin book and doesn't once comment on my idea of an evoIII head. I was kinda hoping to see some feedback. shux

Re: Which Cylinder head?
 

I like the 2G head, it seems to make good power. The 2G intake manifold and 2G throttle body suck though. I wouldn't run it in a performance application without doing a 1g TB and sheetmetal intake though. The 1G heads will "flow" more, but that doesn't mean they will make more power. A smaller port can often do a better job getting more air into the cylinder, due to velocity than a big port that flows a lot on a flow bench.


You will still have to deal with knock.


There was a test done on a turbo Honda with 10.0:1 compression versus 9.0:1 compression on the same car. At 10.0:1 it made a little more HP at the same boost level, but they could obviously run a lot more boost with the 9.0:1 pistons. Turbo spoolup time wasn't really affected at all.

You are going to need some big injectors and possibly 2 fuel pumps, if you plan on making a decent amount of power on E85.

Re: Which Cylinder head?
 

I am very glad you people do... It is getting rare to find people wanting to talk about engine stuff or do anything with engine anymore.


So what I got from niterydr is that there has to be a balance between the port size and the velocity of the air going into the engine. Basicly this all depends on the hp of the car. I didn't know about the term "sonic choke", good thing to know.


I should have used a subject matter like this I should have used a better example then 2g vs 1g. Yes they both use a 4g63 but when it comes down to it, there are a lot of changes between the 6-bolt and a 7-bolt 2g engine.


The whole tuning theory is for another thread. Be glad though that I have realized that instead of using some cheep tuning device, I am using a standalone system taking control of everything plus a wideband. Unfortunatly I don't have a ECU that is an Eprom, or the money for dsm link. I compaired prices and features of both and my decision was to go with the MS system. I do realize that money spent on tuning will make this car "perfect" A car won't run right without the proper tune. Money I will save from going with the MS system will probably go right back into tuning the car.

I should pick a turbo now. I have been avoiding picking a turbo because everyone has their own opinions on them. I should figure out what I am going to go with. then match the engine to it. I still don't know what to go with though...

With E85 I do know that I will still be dealing with knock. I should have specified on this more. With running higher compression pistions and running low grade octane (say 91) I will be having problems trying to tune out knock. Like you said, the pros of E are higher grade 105 octane (sorry about the miss information). Question is though, how bad does the grade of E fluxuates? this could completely mess up tuning.



niterydr- I didn't take it as being picked on, and I hope you weren't picking on me too much:).
I hope this thread isn't just to educate me, I hope there are other people getting information about this as much as me.

Re: Which Cylinder head?
 

To the above who posted it. At the shootout, Brent was telling cher amd myself that he had to swap hos ol' trusty head, because it was machined beyond specs. He didn't have another head, so Marco gave him a 1g head. He left the porting alone, but obviously swapped in his springs retainers, cams, etc. Ran a 7.13 on the car with it. So, that's were I stand. I'm more worried about the air outside of my motor going in (IE intake manifold-shitty) etc, rather then the dynamics of the 1g head taht currently resides atop my block. I am, however, interested in the theories presented behind al of this madness. Does anyone know of other heads that would/could bolt up, or even be modded slightly to work?

-A. Swift

Re: Which Cylinder head?
 

I don't like the way you put "I will be having problems trying to tune out knock"

No, you really won't. It's the same as tuning a 7.8:1 compression motor, only with less boost. My recent setup was pushing 20psi with the exact same timing and almost same fuel as my old stock motor. Only the stock motor was running 22psi.

Re: Which Cylinder head?
 

You are right. I don't know what I was thinking when I made that comment. For some odd reason I was thinking if i were to run the same boost pressure, not even thinking I should be turning down the boost. There is a trade off there.

I forgot to answer what I made my boost controler out of,
T fitting from an air compressor. On the top part of the T, there is a screw that controls the tention of the spring and the spring rest on a little metal ball, like the size of a bb. The bb ofcourse blocks air off untill it reaches a certain pressure where it lets air travel to the bottom of the T and that goes to the waste gate. I have a picture. I should just post it. less then $20.00!

What other questions did I miss, The hard pipes are SS (i will measure it later). I am not sure how the end tanks on the FMIC are going to work, they will work but I just don't know how well... I don't know if I like the design... It is a greedy core with for a 2g with the end tanks cut off and some new ones welded on to fit a 1g. I know there was a big discussion on end tanks not too long ago.

On the hard pipes, there is a flange designed for a DD blitz blow off valve. Came with the intercooler and hardpipes. I think I am going to have to change the spring so it handels over 18 psi. I haven't seen too many people use them so I don't know how it will work.

Just want to say thank you for clearing up a lot of miss information for me. I feel kind of dumb asking questions like these sometimes but it is the only way I will learn on how stuff works!

Re: Which Cylinder head?
 

This has been an interesting read. I've done it in stages so forgive me if I missed this, but... Has anyone asked whether this is even worthwhile? I'm sure there are tons of variables that go into the performance differences in the various head (4 mentioned so far), but I'm thinking that outside the world of theory or huge builds this is a useless subject. If there's no large and clear advantage to one or the other why not just leave the stocker on and invest the time and money elsewhere?

Maybe I'm off base saying "what's the point," but if it were me I could come up with a few dozen things to spend my money on before worrying about the minor theoretical differences that would justify a head swap.

Re: Which Cylinder head?
 

About those Blitz DD's. Every single person I know that owned one sold it because it leaked. I'm not saying don't try yours, because it very well could work. I'm just giving you a little forewarning if you haven't bought it yet.

Re: Which Cylinder head?
 

You'd be amazed at what CFD modeling can tell you in terms of how much a shitty port job can really hurt you.