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D1sc 3.40 pulley twin 4.5 intercoolers...... Boost concern.. 370ci ported 317 heads fast 102 custom cam only making 12 pounds was thinking 15 pounds would be more accurate. Linear gains but flattens out up top. Dont see Belt slip but not sure..
Well a set pulley ratio really sets the air flow of a compressor. Boost is a measure of restriction to that air flow. If you have a pretty good flowing engine it will show less boost even though its flowing the same amount of air. So take a stock engine for instance would show the 15psi your looking for but a modified engine (with cam and heads) will show less boost because it flows the air more easily. Usually even though it shows less boost the modified engine makes more power and torque.
Well a set pulley ratio really sets the air flow of a compressor. Boost is a measure of restriction to that air flow. If you have a pretty good flowing engine it will show less boost even though its flowing the same amount of air. So take a stock engine for instance would show the 15psi your looking for but a modified engine (with cam and heads) will show less boost because it flows the air more easily. Usually even though it shows less boost the modified engine makes more power and torque.
All facts and exactly what I was thinking. It still doesn’t address the low power numbers for what looks like a maxed out d1sc on what should be an efficient combo. It’s possible the belt is starting to slip up top where power flat lines early. No way that thing should stop gaining power at 5800 rpm like that.
All facts and exactly what I was thinking. It still doesn’t address the low power numbers for what looks like a maxed out d1sc on what should be an efficient combo. It’s possible the belt is starting to slip up top where power flat lines early. No way that thing should stop gaining power at 5800 rpm like that.
sorry you are right. I answered without looking at the dyno graph. Just figured this was a misunderstanding if what was calculated and what he got. Didnt do my due diligence.
I would agree a tabletop like that is most likely belt slip.
sorry you are right. I answered without looking at the dyno graph. Just figured this was a misunderstanding if what was calculated and what he got. Didnt do my due diligence.
I would agree a tabletop like that is most likely belt slip.
No reason to be sorry you were correct in what you said. If we could see a boost curve that would tell the story. If it climbs steadily to 12 psi and then the boost quits climbing at 5800 rpm where the hp graph lays over then it's most likely belt slip.
All facts and exactly what I was thinking. It still doesn’t address the low power numbers for what looks like a maxed out d1sc on what should be an efficient combo. It’s possible the belt is starting to slip up top where power flat lines early. No way that thing should stop gaining power at 5800 rpm like that.
Agreed! I was planning to make power to about 7k. Do you think adding a cbr 8.65 crank pulley along with a bigger 3.85 blower pulley would help make a difference? Blower should still be maxed out. Better belt wrap along with larger pulleys?... Thanks
Agreed! I was planning to make power to about 7k. Do you think adding a cbr 8.65 crank pulley along with a bigger 3.85 blower pulley would help make a difference? Blower should still be maxed out. Better belt wrap along with larger pulleys?... Thanks
Absolutely yes larger diameter pulleys help a ton.
Absolutely yes larger diameter pulleys help a ton.
That pulley combination would set the blower rpm at 64880, Would this cause any change in how the boost comes on and do you think that could make more up top?
That pulley combination would set the blower rpm at 64880, Would this cause any change in how the boost comes on and do you think that could make more up top?
If you spin the blower the same RPM then nothing should change except you will have more belt wrap. This "should" increase your boost and as a result you "should" see your hp do the same as it's doing now except at 5800 rpm where it levels off it should continue to climb all the way up. This is assuming two things...one your issue is actually belt slip and two that the additional belt wrap solves that belt slip issue. You should see a continuous rise in boost all the way until your shift point with a procharger.
If you spin the blower the same RPM then nothing should change except you will have more belt wrap. This "should" increase your boost and as a result you "should" see your hp do the same as it's doing now except at 5800 rpm where it levels off it should continue to climb all the way up. This is assuming two things...one your issue is actually belt slip and two that the additional belt wrap solves that belt slip issue. You should see a continuous rise in boost all the way until your shift point with a procharger.
Ok thanks for the replies! Do you have any idea how much of a gain would be possible, maybe 2 more pounds?
Ok thanks for the replies! Do you have any idea how much of a gain would be possible, maybe 2 more pounds?
We're still assuming the issue is belt slip. It looks like boost quit climbing at 5800 rpm so if it is indeed just belt slip and you can fix that then I'd expect another 2-3 pounds easily by 7000 rpm. I'd be more concerned with power gains which 2-3 lbs should put you over 700 rwhp easily. Again I'm only guessing from an internet post description that belt slip is your issue. Definitely worth running larger pulley's either way so running a larger crank pulley is a good start.
We're still assuming the issue is belt slip. It looks like boost quit climbing at 5800 rpm so if it is indeed just belt slip and you can fix that then I'd expect another 2-3 pounds easily by 7000 rpm. I'd be more concerned with power gains which 2-3 lbs should put you over 700 rwhp easily. Again I'm only guessing from an internet post description that belt slip is your issue. Definitely worth running larger pulley's either way so running a larger crank pulley is a good start.
700whp was my target as was 15lbs!
I am going to go with the 3.85 blower and 8.65 cbr crank and see what happens. What belt would you recommend and whats the best way to figure out sizing with the larger crank pulley?
When ordering a HD green belt the letters HD is the suffix at end of the part number. RPM is the suffix at the end of the RPM product line part number. The RPM belts don't stretch like the green belts do (read link). Do not over tighten the RPM belt. No need to because it will not stretch like the green belt.
For example: Gates K080537HD is the HD green belt. Gates K080537RPM is the RPM product line. Eight stands for 8 ribs - 537 stands for length in inches (53.7).
IMO when approaching the 700 - 750 rwhp threshold a quality FMIC is better than two 4.5 intercoolers, especially if you live in states where summer temps are north of mid 90's to 100 degrees and up.
FMIC dimensions for 700 RWHP is typically 26 X 12 X 4 or 4.5 with three inch inlet and outlet. FMIC type should be bar and plate.
Tip: If you don't have an Aster bracket tensioner to reduce belt slip, you can add a fixed pulley to increase belt wrap and reduce belt slip.
When ordering a HD green belt the letters HD is the suffix at end of the part number. RPM is the suffix at the end of the RPM product line part number. The RPM belts don't stretch like the green belts do (read link). Do not over tighten the RPM belt. No need to because it will not stretch like the green belt.
For example: Gates K080537HD is the HD green belt. Gates K080537RPM is the RPM product line. Eight stands for 8 ribs - 537 stands for length in inches (53.7).
IMO when approaching the 700 - 750 rwhp threshold a quality FMIC is better than two 4.5 intercoolers, especially if you live in states where summer temps are north of mid 90's to 100 degrees and up.
FMIC dimensions for 700 RWHP is typically 26 X 12 X 4 or 4.5 with three inch inlet and outlet. FMIC type should be bar and plate.
Tip: If you don't have an Aster bracket tensioner to reduce belt slip, you can add a fixed pulley to increase belt wrap and reduce belt slip.
Thank you for the info! Which belt do you prefer HD or rpm? What's the best way to measure with the bigger crank pulley?
I agree a fmic would be better I just dont want to cut anything up there and dont want to worry about blocking ac and radiator since its a street car.
I've always used the Green Belt and just recently installed the RPM product line. Those users who have switched from green to RPM swear by it, especially on Magnuson chargers.
I recently had my Procharged D1 TSP 370 on the dyno for tuning nearly for 5 hours (Dynojet load bearing Dyno). Friction causes heat and heat causes the belt and the pullies to get hot if the belt is slipping. What I noticed is that the RPM belt was barely warm to the touch after many pulls. So IMO Gates claim that the RPM belt construction is less likely to get hot, slip, and then stretch is accurate. Search this forum for reviews for 'Gates RPM' super charger belts.
However, an Aster Bracket helps to avoid belt slip as well. I have an Aster Bracket and also added a larger idler pulley as well to replace the smaller Aster idler pulley.
The RPM product line is pricey, however, compared to the HD product line. For the belts I mentioned in previous post, the RPM cost from Jegs was over twice as much compared to the HD belt thru Amazon. My RPM belt size was hard to find in stock so had to wait two weeks to arrive.
Send an email to Bob at Brute Speed for belt sizing for the 7.65 and 8.65 pulley or his sticky below in link. Bob handles the HD green product line as well as Procharger belts.
The link is for those that use the Aster Bracket. You might have to use a paper yellow tape to measure belt length. My local belt jobber let me test several sizes before adding the Aster bracket. They let me return those that were too long or short. That said RPM belts are rarely in stock so that's not an option.
I also just installed an 8.65 pulley and will run a 3.9 SC pulley. Since the RPM is so pricey I ordered the HD belt size as trial for fit. If both fit, will always have a spare if I have to replace the RPM belt in the future. With the Aster bracket, switching from a 7.65 to 8.65 with a 3.9 pulley I went from the Gates K080525 to a longer Gates KO80537RPM. That's about 1.2 inches longer with room to move the larger middle idler pulley from the middle hole to the outer hole if needed.
As for the FMIC. There is plastic shrouding in front of the ac condenser and radiator. The shrouding is there to maintain good air flow up from the air dam. There is little if any air that reaches the condenser and radiator thru the bumper cover. In fact if the Camaro front bumper cover is opened to let air pass to the FMIC, the shrouding aft of the FMIC is blocked by the shrouding from passing to the condenser and radiator. Do NOT remove this shrouding because it acts like duct work to encapsulate all air forced up to the condenser and radiator from the air dam.
TIP: I will be posting some pics of a guide bolt that I use when installing and removing the Procharger head unit. The guide bolt keeps you from dropping the charger when installing and removing the head unit. It's a snap to remove and install the mounting bolts with the guide bolt holding the head unit in place as you remove the bolts or install the bolts. You don't want to drop the head unit on the floor - it's heavy and hard to maneuver if installing a new belt.
hth
Last edited by dlandsvZ28; Nov 28, 2020 at 04:24 PM.
Reason: edit content
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Procharger boost help 
