2G Smaller cam for bigger turbo

[2gjlc]

I wanted to hear some thoughts on running a smaller cam to get back some spool time when upgrading to a larger turbo. My mod list is up to date. I have a 2.3 with GSC S2s and a HX35. I've reached the limits of the turbo in the bolt on housing and I'll be moving to a 60mm HX40. This is a street car and I'd like a broad powerband. I could be wrong but from what I've read it seems the turbo will affect the powerband much more than the cams. So would going to a set of S1s or similar kelfords help a little with spool? I lost about 400rpm in spool going from some Comp 100s/FP1s to these S2s and it was a great trade off for the mid and higher rpm power on the HX35. Would adjustable cam gears be a better option? I've read the thread that discusses cam timing and adjusting the cam gears to get back some spool so if these cams are better suited for my application with cam gears I'd consider that. Thanks

 

[biglady112]

You want to play, you have to pay. When dealing with a tiny engine you cannot have your cake and eat it as well. Put the biggest cam(S3) in and thank me later. Absolute hearsay a cam is going to make that kind of a change in a 4g63. Your turbo selection determines your torque curve. Not your camshaft.

 

[2gjlc]

You want to play, you have to pay. When dealing with a tiny engine you cannot have your cake and eat it as well. Put the biggest cam(S3) in and thank me later. Absolute hearsay a cam is going to make that kind of a change in a 4g63. Your turbo selection determines your torque curve. Not your camshaft.

Thanks for the input. What kind of change are you refering too? Shifting the powerband or helping with spool? Not questioning your input just trying to learn. When I had the car dyno'd a few months apart I did loss some spool after a cam swap like stated. This was on ER's dynojet. I think I have the photo of the two dyno sessions uploaded in my pics here. Only changes were cams and some meth. Thanks again.

 

[biglady112]

If you can feel 300rpm on the street, you are either paying far too close attention the it and the Dyno sheet or you are a better man than me. You absolutely should not notice that. You should however notice all the power it gained out the back from those pictures.

shifting your powerband and gaining or loosing spool are the same thing. Only two things will affect that. Displacement and turbine size.

If you cut your own legs off by going down in camshaft timing but up and to the right in turbo size, why bother? Again, you cannot have. Your cake and eat it too. You want “spool”, get a 16g. You want torque, get a real motor. You want to make more power and man up and use what you have, move to a T4 based HX40 and just realize you have to drive it like you stole it now. If not, leave it alone and be happy.

adjustable cam gears will not fix what you are looking for. Take it from someone who has tried to use them on the Dyno. Every car did better with the cams straight up or at true zero(correctly degreed) than anything we could conjure up on the Dyno.

 

[2gjlc]

If you can feel 300rpm on the street, you are either paying far too close attention the it and the Dyno sheet or you are a better man than me. You absolutely should not notice that. You should however notice all the power it gained out the back from those pictures.

shifting your powerband and gaining or loosing spool are the same thing. Only two things will affect that. Displacement and turbine size.

If you cut your own legs off by going down in camshaft timing but up and to the right in turbo size, why bother? Again, you cannot have. Your cake and eat it too. You want “spool”, get a 16g. You want torque, get a real motor. You want to make more power and man up and use what you have, move to a T4 based HX40 and just realize you have to drive it like you stole it now. If not, leave it alone and be happy.

adjustable cam gears will not fix what you are looking for. Take it from someone who has tried to use them on the Dyno. Every car did better with the cams straight up or at true zero(correctly degreed) than anything we could conjure up on the Dyno.

Awesome explanation. Thanks for taking the time. Makes a lot of sense. I think I'll stick with the S2s for now and see what this HX40 does before upgrading cams again and you're right, there is no way ill feel the spool difference on the street or at the track. Found the old dyno graph that shows the spool difference and the car falling on its face on the top end. The car has had a few changes since then to help it hold power up top a little more but I am just not satisfied with mid 400s on this setup.

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[biglady112]

An electronic boost controller and short runner intake will fix most of your curve. Larger camshafts will make the back half come up even more as well.

looking at your mod list, you have the controller. Moving out of the shitty Bolton housing will help as well. Why people still waste their time with those housings 20-25 years later is still beyond me. Not a single other car community limits themselves right off the bat like that.

 

[2gjlc]

I am with you on the housing being the main limiting factor. I'll definitely be moving away from it but it was made for a fun street setup especially when it was on my old 2.0 motor. Between the housing and poor octane in California it is harder to make good power. I remember being at English Racing for a tune and hearing them joke about how terrible the fuel is out here. T3 or Twin Scroll T3 is in my future for sure. You're right on the money with the 3 port boost solenoid. I got retuned at RRE with it and it is amazing what they can do with the boost curve. The change from that and to an Evo 3 intake allowed me to hold power up top much better but the dam turbine housing is hurting me. Here is a graph of that dyno session. Not really an apples to apples comparison since ER has a dynojet and RRE uses a Dynapak. Torque is in the 420s now but I don't have a good image of that tune.

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[biglady112]

The intake did nothing for you. The curve is still the same shape and falls off when a factory intake normally does. Your pump gas is no different the my pump gas. The fuel in general is not ideal for forced induction tuning.
I tuned a friend’s car in the LA area last month. Two cars actually. The car with the bigger turbo and pump gas made 100hp less than the car with the smaller turbo on E85.

The bigger turbo car had a goal of 400 on pump gas. I literally did that at 24-25psi on a fp3065. The other car was a S257 in a t4 housing. He made 480hp@32psi maxing the turbo out.

The 3065 had a short runner intake and mostly rose until 8100-8200 then fell off. It had a manual controller though. The smaller 257 car had a stock intake and an electronic controller and his power came up and stayed flat until I let off even with the stock intake. His torque fell but, the power never did. Both cars had small cams.

Tuning was done on a mustang Dyno I feel was very honest.