Intake manifolds revisited

[cheekychimp]

I have searched, quite a lot in fact but it seems the jury is out on this one, so I figured I'd play devil's advocate here a bit in the hope of promoting a healthy discussion. I'm hoping for some reasoned explanations, real world experiences and educated debates ... we'll see what happens.

Right, putting my 'unorthodox' turbo choice aside for a moment, I set out to build my car for torque and a powerful low/midrange. That was why I went with the stroker and chose the Forrester intake over a SMIM.

The Forrester has a very reasonable reputation and is supposed to give an improvement in midrage and top end without sacrificing any low end torque. So sounds ideal for my application. But then I sat and thought that the Forrester was designed around a US spec manifold, so whilst the Forrester might not have any worse performance than a stock 1G or 2G manifold, would it be better for spooling a turbo than the cyclone manifold.

Since I really don't expect to spend much time over 6500-7000 rpms I wondered if I should consider trying the cyclone. My mechanic immediately told me that even if I machined the cyclone to accept the larger throttle body it would become a restriction to my larger intercooler pipes and headwork I have had done. He assures me the Forrester is the biggest favour I can give my big turbo and will help spool up much more than the cyclone.

So, if I want huge torque, full boost at 3000 rpms and I don't care about top end airflow, am I doing this all wrong? Should I have gone 2" with the intercooler piping, stuck with the stock cyclone intake and left the head stock, or are the big bore pipes, spacious intake and polished/ported head going to work in my favour.

Discuss.

 

[atc250r]

IMHO trying to get a DOHC 16V motor to make a lot of low end torque is going against the very nature of the beast. If I was looking for a lot of low end I'd build a big V-8 or something with a lot more cubic inches than a 2.0, 2.3, or 2.4 engine. When I put on the Driven Innovations intake I can honestly say that I didn't notice any decrease in low end and I think I may have even picked up a little. The Cyclone is a great set up and I'm not going to bash it at all but it would probably work best for a smaller turbo'ed car like a 14B or and of the 16G's.

John

 

[slugsgomoo]

If you want torque, the recipe seems to be 2.4L, 2g Head, medium sized turbo. /ubbthreads/images/graemlins/dunno.gif

Frankly I'm guessing your turbo will have more to do with your spool than your other mods at this point. Don't you have some sort of holset/bullseye or something?

 

[powerplay]

I can only speak from what I have and know. I have a stock head and TB, E3-16G turbo, Cyclone manifold. The manifold, without a doubt improved the low-end torque. The car is easier to drive on the street, you don't have to shift gears as often. I can't provide before and after numbers, as I don't have any. But other people have driven the car and noticed the difference in the ability of the engine to pull from lower RPMs. It just makes it easier, (lazy, less shifting)to drive. I haven't noticed anything else about the difference between a stock manifold vs the Cyclone.

 

Its all about port velocity.

Ginormious intake ports will make gobs of power up high but, the low end and response will suffer.

Smaller intake ports will make great low end be more responsive but, max flow/ max power will suffer.

I would think a extruded/match ported cyclone would be a great manifold to get the best of both worlds.

If the butterfly's could be enlarged and the engagement point of the secondaries tuned, it might be a very nice addition to a duel purpose motor.

But arnt you using a HX40/35 turbo?
I don't know if I would use the Cyclone with that.

Might be best to stay with the big port manifold/head combo and spend more time focusing on making the engine spin up faster ie; less rotating mass.
This should decrease the amount of time it takes the for you to get into your engines sweet spot.
Combine that with chassis weight reduction and you should be getting up to speed pretty quickly. IMO

You might want to look into gearing as well.
RS trans maybe???


I understand what your tiring to do though.
If spent allot of time milling things over in my head before purchasing components for my AE86/4G63T project.
I ended up going with a mildly ported 2G head, and a reworked ported 2G intake manifold to increase the port velocity vs a 1G head and intake manifold.
I believe this setup combined with FP-1x cams, and the lightness of the Corolla chassis will make a very responsive machine.
(my new problem is tire size vs exterior aesthetics /ubbthreads/images/graemlins/banghead.gif)

 

That's sort of the setup I'm running. 2.3 with an agp L2R and a cyclone manifold. I tried a magnus just to see the difference, and you do give up some top end, but the lower RPM improvment was well worth it to me. I would think you'd be better off with a smaller turbo though, hx35 would be as big as I would go with the holset line since the manifold is going to choke the extra flow the hx40 impeller provides. With the 35 I'd think you'd have a really wide powerband and a topend in the upper 400hp range. Seems about perfect as far as a street car goes to me.

 

[skivittlerjimb]

Bob's 2.3l torque monster with stock intake manifold.

I'm sure you've seen this before, but it bears repeating, as it seems you and Bob had/have similar goals.

-Jim B.
1432/2000
167k

 

Friend of mine is making 400/400 with his 2.4 50trim at the wheels on a dyno dynamics (think lower readings then a Mustang). We set it up RIGHT, and we aren't even talking a ton of boost yet either.

 

[OldHairyBastard]

Use a little bit of spray for the low end torque and you will not be disappointed. I'm not talking a lot just like a 30-35 shot. If your looking to only go all turbo then that set up should be fine but the spool won't be until the upper part of 3,000 RPM. The 4G63 is just a dog until the turbo kicks in. That's how they were built--for boost. The stroker helps a lot but unless you go with more compression then your stuck with no power till boost. If you took off the turbo on these cars it is like going from a full out attack dog to a scared tea cup poodle. That is just the design--Boost is the replacement for the displacement and lack of torque--you have to have a little for-play before the boost comes in unless you go with a roots type blower and turbo. With the roots type TRD blower on my Camry there is no for-play. When you nail the gas the power is right there and the sound is music to my ears.

Doug

 

[cheekychimp]

Guys, thanks for the replies, this was better than I had expected.

Quote:
The Cyclone is a great set up and I'm not going to bash it at all but it would probably work best for a smaller turbo'ed car like a 14B or and of the 16G's.



John, this makes a fair bit of sense. It seems to me what you are saying here is that the manifold was designed to flow roughly the maximum airflow the stock turbo was capable of flowing with the secondaries open, so that the opening point of the butterflies was precisely designed to match the point at which airflow exceeded the limits of the shorter runners. I'm guessing with a bigger turbo that limit might be exceeded much faster making the butterflies a restriction as the turbo was trying to get into it's stride.

Quote:
Might be best to stay with the big port manifold/head combo and spend more time focusing on making the engine spin up faster ie; less rotating mass.



Yes, I see that logic and fortunately I think I have this covered. 2.3 litre, 9.0:1 compression, lightened knife edge crank, no balance shafts and aluminium rods.

Quote:
hx35 would be as big as I would go with the holset line since the manifold is going to choke the extra flow the hx40 impeller provides. With the 35 I'd think you'd have a really wide powerband and a topend in the upper 400hp range. Seems about perfect as far as a street car goes to me.



Yes, I debated this issue for quite sometime. Some people said the HX-35 was too small for a stroker others like yourself said 400 hp was about as high as I should aim for if I intended to get the car to handle and corner well. I ended up with the Hybrid because I felt it would fall halfway between the two. We'll see.

Quote:
Use a little bit of spray for the low end torque and you will not be disappointed.



Doug, I hate to sound like a newbie but I have never understood this. I thought nitrous was not supposed to be injected until a vehicles engine was already running quite high rpms and that injecting under load too early was a recipe for disaster because too much gas found it's way into the combustion chamber. So how is this actually done? Is the idea to spray pre-turbo so that the expanding gas spins the turbo up prior to boost being made?

As for everyone else that chimed in, again thanks for the comments. Bob's car is very much what I was aiming for with possibly a little more power. Certainly seems that the 50 trims are very well sized street turbos and it is interesting to note once again that whilst dynos often show the stock manifolds tapering off at about 6500 rpm that a) most street cars spend very little time above that rpm level and b) people are still making good power and running respectable track times in spite of this. Which is why given that I rarely expect to be able to take advantage of the top end of a big turbo in Hong Kong I wonder how much of a restriction a stock or cyclone manifold would actually be.

On a final note, Sgt Dave also said:

Quote:
I would think a extruded/match ported cyclone would be a great manifold to get the best of both worlds.



I've lost count of how many times I considered doing exactly this!!!

 

[OldHairyBastard]

You are correct. You need to be at least above 2,000 RPM before you should spray. I would say to be at 2,700-3,000 RPM just in case. I like the fact that this little amount of spray can give you even more then 35 HP when a turbo or supercharger is involved. With only a 35 shot you can start it around 2,700 RPM on a window switch and leave it on through the whole run and or just arm it when you want. It will only activate after you arm it when you are at WOT-Wide Open Throttle above the RPM turn on setting. This works really well and you don't always have to have it on-only when you need it or WANT IT!!! A 35 shot will give you at least 35 to the wheels with that turbo. I've had a number of people tell me that bottles are for babies and then I-depending of where I'm at-point the the beer in their hand and say is that so.--I like having spay in order to cool down the intake air temp as well, but I do like to have a separate system for the fuel running to the nozzle and high octane running to it to help out even more and for the timing issue. Here is a whole system for sale Spay .

Doug

 

[cheekychimp]

Quote:
You are correct. You need to be at least above 2,000 RPM before you should spray. I would say to be at 2,700-3,000 RPM just in case.



But you are still spraying at the intake manifold/throttle body and not pre-turbo?

Would propane work in the same way?

 

[OldHairyBastard]

Spraying pe-turbo is bad and dangerous. Nitrous explosions happen a lot doing this because if you let off of the gas you still have all the Nitrous in the intake pipes depending on your blow off location and all of a sudden BOOOOOM. You just blew a hole in your inter-cooler and right through your front bumper. I have seen this happen twice right next to me at the track. The first time was a supra from Schaumburg up at Great Lakes Dragaway in Union Grove Wisconsin and the second which was not running on the track and not spraying before the turbo but a solenoid stuck open for about 30 seconds before they could get in the trunk to shut off the bottle on a WRX that Drivers Image had at Great Lakes Dragaway as well. They thought that they let the car sit long enough before they went to start it but never lessened the pipes to let out the nitrous and when the motor started BOOOOOOOOOOOOM!!!! My right ear was ringing the rest of the day. Only a few people had minor injuries nothing bad--They were lucky.

 

[curtis]

Paul. Your holset flows around 65 lbs a min thats what a GT35R flows. You have a raised compression stroker with rods that don't weigh crap. Your not going to have a problem with low end or making the engine wrap up instantly. Put it together with the forrester and run it. You have a good combination and can debate over it forever. The only way to see is to put it in the car and drive. If its to laggy for your tastes then you can redegree the cams and go from there. Your going to have a mean car.

My buddy Spannky here in town has a 60-1 with a 2.0 and a forrester manifold in a front wheel drive talon. The chicken smokes tires at will....Just stop stressing about it.

 

[cheekychimp]

Thanks Curtis ... of all the replies, that's probably the one I needed most!