Forged pistons and rods

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  • I am running a DDM motor with their turbo and a Haltech currently at 480hp

    You can run their turbo on a stock motor and I think 350 hp is the number but I would confirm that with Dave@DDMWorks . No need to build a motor if you run his turbo and teh stock ECU. Trust me that is the outside of usable hp and you should be very happy.

  • I have a DDM engine. I have been trying to kill it for a while now. So far it has held up to everything I have tossed at it. Some people would probably say that I am a bit rough on engines. ^^:D:D


    I am about to give my engine a new toy today. Just grabbed it off the UPS truck. I will have 3 wideband sensors when I get this installed.... I will have the Innovate controller feeding its data into my Haltech and then this WB2 feeding 2 more steams into the Haltech.


    You can't have to much data....


  • IIRC, the conventional rule of thumb for the Ecotec 2.4 motor is a max of 75 HP/cylinder (300 HP) before needing forged rods. Most of the turbo kits sold for the Slingshot for use with stock motors safely fall under that limit. The closer you get to 300 or more HP, the more likely you are to encounter problems on a stock motor. IIRC, the Pontiac Solstice and Saturn Sky used forged pistons on their 2.4L motors for a couple years, making those years a good block for rebuilding/boosting, but later motor castings have some improvements to cooling cast into the blocks. Most of the engine builders for the Slingshot use or offer the improved blocks.

  • What the hell are you up to now?

  • IIRC, the conventional rule of thumb for the Ecotec 2.4 motor is a max of 75 HP/cylinder (300 HP) before needing forged rods. Most of the turbo kits sold for the Slingshot for use with stock motors safely fall under that limit. The closer you get to 300 or more HP, the more likely you are to encounter problems on a stock motor. IIRC, the Pontiac Solstice and Saturn Sky used forged pistons on their 2.4L motors for a couple years, making those years a good block for rebuilding/boosting, but later motor castings have some improvements to cooling cast into the blocks. Most of the engine builders for the Slingshot use or offer the improved blocks.

    Does this apply to Superchargers as well? I’m pretty sure your not exceeding 350hp with a SC but was curious about heat build up and exhaust sizing as well. I’m currently running welter duals (2.5”).

    What the hell are you up to now?

    Good question! Do tell Rab!🤔

  • I can confirm what has been said about the HP numbers. I have been running an unforged motor safely at 350 HP dynod at the wheel. My set up is the DDM Supercharger with Cams with an updated tune.

    rabtech   MACAWS and my self have beetin our engines pretty hard to validate the 350 HP number unforged.

    As anyone who has been in my sling will tell you, I bounce the rev limiter regularly with some reckless abandon.

    Thank Dave@DDMWorks for the great products.

  • I can confirm what has been said about the HP numbers. I have been running an unforged motor safely at 350 HP dynod at the wheel. My set up is the DDM Supercharger with Cams with an updated tune.

    rabtech   MACAWS and my self have beetin our engines pretty hard to validate the 350 HP number unforged.

    As anyone who has been in my sling will tell you, I bounce the rev limiter regularly with some reckless abandon.

    Thank Dave@DDMWorks for the great products.

    Hope you can join us in Bristol.....

  • We do not push past 9psi on a stock bottom end with our turbo builds. 9psi is typically 300whp on 93 octane on a Mustang dyno. People say they read 15-20% lower than other dynos so split the difference and call it 350whp. ZZP has a Gen 3 forged internal short block that we sell. You can check it out here https://zzperformance.com/coll…3-forged-2-4l-short-block We also ship the engines for free via freight within the US or if you wanted us to do the install we are more than happy to do that as well.. If you wanted a long block we can definitely build one up for you and in that scenario, there are many options as far as keeping things stock or upgrading different parts. This is the same block I am running making over 500whp. If you want to discuss build options, feel free to email me directly at Kyle@zzperformance.com

    ZZPerformance EST 2000 - Go Fast Not Broke

  • I can confirm what has been said about the HP numbers. I have been running an unforged motor safely at 350 HP dynod at the wheel. My set up is the DDM Supercharger with Cams with an updated tune.

    rabtech   MACAWS and my self have beetin our engines pretty hard to validate the 350 HP number unforged.

    As anyone who has been in my sling will tell you, I bounce the rev limiter regularly with some reckless abandon.

    Thank Dave@DDMWorks for the great products.

    Slingrazor , what exhaust are you running? I have heard that the welter duals (2.5”) are borderline small once over the 300hp range on a supercharged motor? I’ll be making a lot of changes this winter and would also like to confirm this. I’m happy to hear you are running strong on stock motor. I beat the hell (100mm pulley) out of mine as well but after having a piston failure I’m trying to figure out what I need to change.

  • I have been running the Welter2.5 Sidkick for 2 years with no problems. I burned up a custom Magnaflow and an Alpha Side exit before the Welter.

    I am running a 95 pulley with the cams. I also installed ARP head studs for insurance against the head liftung and taking out a piston.

    What I have learned for the engine failures with the SC not get into the throttle below 3000 rpm above second gear. Off the line, first and second gear I will stomp the throttle at any time. Above 2nd I do not mash the throttle and lug the engine below 3000 rpm. The failures I know of did this in fourth and fifth gear due to heat soak in the pistons causing failures.

    If you have any questions, give me a call in the evening. Leave a message if I dont pick up.

  • Thinking about rebuilding my motor. At what horse power should forged pistons and rods be considered? Also thinking about a swap out with DDM’s built motor option.

    There really is not a magical horsepower or boost level that above which forged pistons and rods should be swapped in, just general guidelines that have been observed over time. Different factors like supercharged or turbo, other modifications done to the engine and how it is being ran will all have an effect on when the right time is to build the engine. In general though, above 300hp has become kinda the standard answer for when you should start to consider building the engine. Can you go higher with the stock block? Absolutely. Have there been failures below that level, Absolutely also.


    Keep the heat out!


    That number of 300hp at the wheels had a lot to do with the early Alpha turbo kits and all the failures they had above that horsepower level. As the engine in the Slingshot was not designed for forced induction from the GM. When the engine was designed and built, they chose a piston design that is relatively high compression (10.4:1) with the upper ring land design being relatively thin, with tight ring gaps. All of these design choices were made to make an efficient naturally aspirated application. The problem with those stock pistons are the relatively high compression lends itself to detonation/pre-ignition under boosted conditions, although this problem is relatively easy to control with tuning in the ECM. The thinner upper ring land though and tight ring gaps can still present a problem, especially on turbo applications or long, high load conditions.


    A turbo gets the power needed to compress air from exhaust flow/energy, however the turbine does present a direct exhaust restriction in the flow of exhaust out of the engine. This means that turbocharged engines (I am talking about mass market turbos here/ones used on Slingshots) will have a higher exhaust backpressure than naturally aspirated. This higher pressure in the exhaust side of the engine causes heat and pressure to build up to levels higher than naturally aspirated in the engine. During long runs, the heat will start to soak into the engine/piston and cause the upper compression rings to expand. When the rings expand enough that the ends of the rings touch, if the heat continues, the force builds up and with no where else to go, the force will pop a piece of the top of the piston off. This is by far the most common failure we saw with the Alpha turbos and engine failures in general with the Ecotec engine. Typically it is always cylinder #2 or #3 also, do to the less efficient cooling around those cylinders. There were design choices made with the Alpha kit which did not help and actually contributed to the heat build in the engine, a very small exhaust section that they ran on their turbo. The small exhaust section they chose for their turbo allowed for a quicker turbo response/transition at the expense of causing more exhaust pressure build at higher flow rates.


    The exhaust sections of turbos have what is called an A/R ratio, which is a ratio between the cross sectional area where the exhaust flows and the radius of that spot from the center of the turbo. In general a smaller A/R ratio will give you a quicker responding turbo at the expense of being more restrictive to flow. A larger A/R allows the exhaust to get out easier and make more power, but usually has a slower response. The Alpha turbo kits used a very small .48 A/R ratio, compared to the .64 more commonly used or even the .85 or greater used on some setups. That smaller A/R gave great spool, but of the 50+ engines we documented with failures, almost all of them were do to heat related failures.


    There have been rod failures we have seen also, but those are a very small percentage of cases and were mainly seen with the HAHN kits that spooled pretty fast also, but seem to have an issue with detonation at the lower RPM range and would cause the rod failures. Of all the engine failures we know of here, I would bet we have only talked to or seen about 3-4 of this failure, so the heat related failures are definitely the vast majority.


    The couple of supercharged engines we know of with failures were mainly from heat related issues also. We have had to be much more vigilant with the exhaust options people are running with the supercharge now, as some manufacturers continue to change their exhaust, restricting flow to quiet them down. When they create more exhaust restriction to quiet the exhaust, it builds more backpressure and heat build in the engine also.


    How the engines are ran is also going to make a difference, like Slingrazor said, there are plenty of customers we know that are running into the mid 300's at the wheel on a stock engine, with no issues on both turbo's and superchargers. We have ran short bursts of 400hp on stock 100k mile junkyard engines and been fine also. The stresses from heat that are placed on a turbo engine being ran full throttle for 5 miles are completely different than a supercharged engine at the same pressure running 1/4 mile or even 1/2 mile at a time. We recently had a customer with a GPS verified 191MPH run in one of our turbo/built engine Slingshots, it was a long pull that got him deep into 5th gear, full throttle for a long time with a lot of power/heat. That being said, one person may consider that a hard run and another person might consider running up the engine to 5000RPM and getting to 90mph a hard run, really depends on the point of view. The person running up to 5000RPM and 90mph probably does not need a built engine even with 350HP at the wheel, while the other one definitely needs a built engine.


    I know that probably does not give a black and white answer, as there really is not a black and white answer to give with this question. Hopefully it will give a little bit of a guideline to go by though.


    I know we have talked on the phone a bunch already, but feel free to give a call anytime - 864-907-6004.

    Dave

  • Thanks Dave, I appreciate that info. Also want to say thanks for all the time spent on the phone while I ripped her apart and used the parts you sent to resurrect her for the summer. I recently asked rabtech what his thoughts where on a built motor at my power level. By the end of our conversation he had me seeing dollar signs and 450+ horsepower. Lol!!! Beast mode. When putting it back together I did use ARP head studs but am kinda kicking myself in the ass for not taking the opportunity to go forged. I drive pretty hard and shift at Red line 95% of the time. This winter I will Be making changes but need to decide which route I’m going.

  • Thanks Dave, I appreciate that info. Also want to say thanks for all the time spent on the phone while I ripped her apart and used the parts you sent to resurrect her for the summer. I recently asked rabtech what his thoughts where on a built motor at my power level. By the end of our conversation he had me seeing dollar signs and 450+ horsepower. Lol!!! Beast mode. When putting it back together I did use ARP head studs but am kinda kicking myself in the ass for not taking the opportunity to go forged. I drive pretty hard and shift at Red line 95% of the time. This winter I will Be making changes but need to decide which route I’m going.

    I think you have a pretty good plan going forward with enjoying the summer up there and then doing something over the winter. Also, it sounds like you have some great help up there and should be able to knock it out pretty easily when you do decide to the the engine and cams :thumbsup:

  • I think you have a pretty good plan going forward with enjoying the summer up there and then doing something over the winter. Also, it sounds like you have some great help up there and should be able to knock it out pretty easily when you do decide to the the engine and cams :thumbsup:

    Casey_SS has been a great help. Thanks to him I did not have to get YouTube certified. Lol!! 2 big lessons learned

    #1 don’t drop the timing chain guide bolt in the oil pan. Results in pulling the pan twice. 🤦‍♂️


    #2 make sure the Blow off valve cap is threaded or the spring will go flying into the woods.

  • Dave@DDMWorks you are like a brother but when you say someone has been191mph..... Someone's nose was growing when they told you that....


    I belive noone that says they have been over 145mph. Not without seeing a time sheet...


    And the only way I would belive a speed above 150 on the open road would be to see a video with them showing a run up to 100mph and the speedometer and the GPS readout matching. Then without stopping the recording make the top speed run.


    I know that we are talking about winding it up over several miles. And I understand that what we do is within a 1/2 mile area... I agree that with enough space we might get to 165 or 170 if we had a tail wind and it was slightly downhill. But 191mph in a slingshot!!!! Nope.... It didnt happen without really good video documenting it.