MindIfISmoke's? Built Part 3.
- Thread starter MindIfISmoke?
- Start date
MindIfISmoke?
Wrecking Crew
Yeah I have a whole bunch of shit i need to sell then ill start shopping
toorbeenee
turbine lunatic
JeremyH
3V Fuel Guru
Nice, honestly that looks to be in the tune. Are you using vct and what is timing up top?
If I had to do it over again I would have left the stock cams in.
Yes. he is at 980rwhp with stock cams. That 76mm turbo's transient response/boost threshold is definetly less. I was waiting for what seems forever for it to full spool lol Then again the billet compressor wheels have me spoiled!
Nope, stock heads and cams.
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MindIfISmoke?
Wrecking Crew
Vct is locked out. 16.5° up top. That was on pump
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ZmanM3
The Evil One
Glad you have it back on the road. I have to say that over time I've become somewhat impressed with the stock cams and heads.
MindIfISmoke?
Wrecking Crew
Thanks zman!
garner
Senior Member
There's a local guy that's making 750 with turbo and stock cams, intake, exhaust, and throttle body. So I don't think you'll need cams
jodadejss06gt
TEAM DELETE SHIT
like marc recommended me, i'd take his advice and do head work to my car before i deal w cams
rford426
Resident 5.0 H8R
cams are overrated just like everyone else has said look at turbo pete...alll he has is upgraded springs and retainers I wanna say...putting down close to 900...You have arp head studs??? Im hoping i can make 650 at 15psi or so...that will be my next tune
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BruceH
BBB Big Bore Boss 322
The stock cams are already ground with 7 degrees of advance. Locking out the vct without retarding them is limiting the top end imo. Have you thought about putting the limiters back in and seeing what happens with some retard up top?
Marc s
NASA AIX
Bruce is right. Locking the stock cams puts them really far advanced and is the reason for the peak HP of 5400 RPM's. Matt needs to either retard the stock cams or replace them so he can extend the RPM range.
MindIfISmoke?
Wrecking Crew
I am using the trick flow springs. They have the exact same specs as the livernois
Marc s
NASA AIX
On Mod motors, I have found that for every 2 degrees you advance the cams, you lose 200 RPM's off of the peak.
Camshafts on turbos are tricky specifically on the exhaust side. A turbo motor has a longer power stroke than an N/A, SC, or N2O motor because the piston forces out the exhaust at higher pressure. I believe the powerstroke is an extra 20 degrees of crank duration. Hard to verify that, but it does stand to reason. This would mean opening the exhaust valve too early would cost you a lot of power.
Typically the restriction in a Mod motor is on the intake side. On an intake restricted setup that has plenty of exhaust flow, if you open the exhaust valve to early you'll end up over scavenging the cylinder and you will get exhaust reversion. Now, when there's plenty of overlap & RPM's are high enough, this is not a problem. The over scavanging helps pull in the incoming air charge. But when there is very little overlap, like on a stock camshaft. And there is extreme exhaust pressure in the exhaust manifold, over scavanging the exhaust can really hurt performance as exhaust gasses will return to the chamber & dilute the incoming aircharge causing a slower reving motor and a HP loss up high. At no time in a turbo application is the intake pressure higher than the exhaust. RPM & velocity through the intake tract can help force out the higher exhaust pressures, but at low RPM there is very little intake airflow velocity so delaying cam timing events becomes very crucial.
One of the things that I had to consider when tuning Matt's engine was the overly advanced stock cam that have very little overlap. Because of the advanced timing event's, closing the intake valve early, increases cylinder pressure significantly. High cylinder pressure on pump gas is a bad thing (see Matt's build thread #2). With a different set of cams or degreed stock cams, I would be more comfortable getting aggresive with the timing tables with pump fuel.
IMO, the only upside to advancing cams is slightly quicker turbo spooling. Again, this is due to trapping the intake charge by an early closing intake valve.
On turbo applications, I've always gained a lot of HP from retarding camshafts that were overly advanced. I believe Matt will see close to 100whp gain from replacing the cams or 50+whp gain from degreeing the stock one.
Camshafts on turbos are tricky specifically on the exhaust side. A turbo motor has a longer power stroke than an N/A, SC, or N2O motor because the piston forces out the exhaust at higher pressure. I believe the powerstroke is an extra 20 degrees of crank duration. Hard to verify that, but it does stand to reason. This would mean opening the exhaust valve too early would cost you a lot of power.
Typically the restriction in a Mod motor is on the intake side. On an intake restricted setup that has plenty of exhaust flow, if you open the exhaust valve to early you'll end up over scavenging the cylinder and you will get exhaust reversion. Now, when there's plenty of overlap & RPM's are high enough, this is not a problem. The over scavanging helps pull in the incoming air charge. But when there is very little overlap, like on a stock camshaft. And there is extreme exhaust pressure in the exhaust manifold, over scavanging the exhaust can really hurt performance as exhaust gasses will return to the chamber & dilute the incoming aircharge causing a slower reving motor and a HP loss up high. At no time in a turbo application is the intake pressure higher than the exhaust. RPM & velocity through the intake tract can help force out the higher exhaust pressures, but at low RPM there is very little intake airflow velocity so delaying cam timing events becomes very crucial.
One of the things that I had to consider when tuning Matt's engine was the overly advanced stock cam that have very little overlap. Because of the advanced timing event's, closing the intake valve early, increases cylinder pressure significantly. High cylinder pressure on pump gas is a bad thing (see Matt's build thread #2). With a different set of cams or degreed stock cams, I would be more comfortable getting aggresive with the timing tables with pump fuel.
IMO, the only upside to advancing cams is slightly quicker turbo spooling. Again, this is due to trapping the intake charge by an early closing intake valve.
On turbo applications, I've always gained a lot of HP from retarding camshafts that were overly advanced. I believe Matt will see close to 100whp gain from replacing the cams or 50+whp gain from degreeing the stock one.
MindIfISmoke?
Wrecking Crew
Thank you Marc! I'm saving cash moneys now for cams.
JeremyH
3V Fuel Guru
STOCK CAMS! Get them degree'd or fuck trick flow and put the limiters back in. lol
MindIfISmoke?
Wrecking Crew
I don't want to deal with all that damn noise!
That's correct.
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