DSM Converter FAQ

What size is the stock 1g and 2g converter?

The industry size would be 11″, but the actual turbine size is 10.25″.

Stock DSM Turbine Size

Stock DSM Turbine Size

 

 

 

 

 

 

 

 

 

Is the stock converter furnace brazed?

Yes and No. The factory brazed the impeller but not the turbine. This means it isn’t as strong or as efficient as if it were brazed.

 

DSM Impeller

DSM Impeller

 

 

 

 

 

 

 

 

 

 

DSM Turbine

DSM Turbine

 

 

 

 

 

 

 

 

 

 

Is the factory stator a high stall or low stall?

It’s actually a high stall stator which is one reason the converter couples in the 6.5% range on 16g type turbos around 20psi. The stator and non brazed turbine are the two main reasons why it’s not like our 9.5″ that sees high 2% to 3% coupling (and that’s on a GT4202 turbo around 40psi).

Stock DSM Stator

Stock DSM Stator

 

 

 

 

 

 

 

 

 

 

Can the transmission pump or trans in general ever hurt the torque converter?

This is the 1 and only time I’ve seen this in a DSM, but yes it can. (This is also the rare time we fixed a stock restall to get a customer back on the road, because we don’t offer restalls).

Stock DSM Stator Damage

Stock DSM Stator Damage

 

 

 

 

 

 

 

 

 

What is a restalled stock converter and what performance gains and losses does it offer?

The reason I got involved in smaller DSM converters was due to the lack of performance (acceleration and coupling) in the restalled stock converter. A restall entails modifying the stator and even impeller vanes in the converter for a higher stall. These mods will increase stall/flash stall a little but at the same time increase slippage up top. The slippage you gained in stall will now lose you mph at the top end. The stock converter is around 6.5% and the restalls add 2% at minimum with some going as high as 20% depending on how modded the internals are and the power level of the engine. Every 3% in slippage is roughly 4 mph.

 

What turbine size matches the stall of the stock restall converter?

In general a 9.5″ converter matches the stall but couples tighter up top netting a gain of roughly 7 mph if it’s 3% vs 9%. If the restall is looser it will stall slightly higher but really give up more mph up top. One example is a big turbo customer of ours had a gutted restall stocker slipping in the 20% range, after going to our 9.5″ he gained 10mph, on 10psi LESS boost!!! That’s a HUGE performance gain.

 

What do the stock 1g and 2g converters weigh?

1g = 24lbs

2g = 34lbs (lock up clutches and taller height)

 

Does weight have any advantage in stalling up the engine?

Yes, weight adds a load on the engine which helps the turbo spool up. Ever try to spool up in neutral, exactly, you need a load and of course torque.

 

Is the question above the reason you can add weight to your DSM Spoolinator converter?

Yes, the smaller converters weigh less so we try get them closer to the factory weight for even more stall. The end result is roughly…….

8″C2 = 21lbs

(We no longer add weight to the 9″ and 9.5″ since they’re close to the stock 1G weight and the hardship on our machines to shape the weight.)


I have a small turbo combo with the stock converter and want to run the fastest E.T. possible, is there any gain to switching to a smaller converter?

Yes, a 9.5″ and 9″ will run quicker and faster. You’ll gain the quicker E.T. because the smaller converter will stall/flash stall higher and faster (acceleration) getting the car moving quicker to a given distance vs the slower converter. The smaller converter also has a shorter rpm drop on gear changes (keeps you in peak power longer) so the car is coupling in your peak power band vs lugging you down too far in rpm.

The faster aspect is because the 9.5″ and 9″ couple the power tighter up top and put more hp to the tires = more mph. The stock converter isn’t a better performance option vs a smaller converter, you’re not maximizing the cars potential with the stock converter, there is an easy .4 in ET being lost by the stock converter in this small turbo scenario. There is way more E.T. lost as the combo gets bigger due to horrible acceleration from the bigger converter.

 

Why won’t the stock converter stall up my 58mm turbo high enough to leave hard? 

Simply put, the stock converter at 10.25″ is WAY too large for a performance DSM, even the Drag only 75mm turbo cars. This turbine size with a different stator would couple 1200-1500hp big block cars without much issue. You want a converter turbine size that can couple your potential power and be small enough to stall up the combo fast. Our 8″C2 Spoolinator would easily stall up this combo without nitrous and is large enough to couple the power. That’s why it’s the non nitrous DSM record holder at 8.93 E.T.

 

Why would a car company use the stock converter then?

Because this size couples sooner in the rpm band and is more efficient at lower rpms where most engines run at = gas mileage. The gain isn’t as big as you’d think but even a 1 mpg loss can hurt car sales. In my old 99% stock 1g Dsm I’d see around 70mph at 3000rpm on this strip of the highway I frequently use. Our Spoolinator in my 2nd 1g sees 67mph at 3000rpm on the same strip so there is a small loss in that range (Spoolinator is still in its stall multiplication range). But can the stock converter stall to 4500rpm with a 62/66, FP2 cams and a JMF Race Intake? Nope, I’ll take the tiny loss in gas mileage vs being a snail on the launch.

 

I notice my restall stock converter only nets around a 22mph gain after the 1/8 mile (104mph 1/8th – 126mph 1/4). Is this normal?

Yes, for a restall. Our Spoolinator and 9″ would net around 4-5 mph more in this scenario = 130mph (9.5″ is tighter but only for small turbos or huge ones with tons of nitrous). In essence you paid to gain the better 60ft but lost the equivalency of a cams upgrade at the top end. Then take into account that both the 8″C2 and 9″ offer better acceleration and you’ve lost at least .8 in E.T. by using a restall and more in certain scenarios where you can’t even stall up the combo (62mm turbo netting a 2.4 60ft vs a 1.4 is a minimum of 2 seconds in E.T.) The smaller converters are quicker and faster, this has been proven for decades on other platforms and we’ve custom made it a reality for the DSM crowd to experience for themselves.

 

Are there any mods to help my car stall your torque converters higher?

Part 1 = Brake mods. Hear me out here, a transmission brake isn’t going to happen for the DSM community (I could get one made but the costs are high and the community insists they aren’t needed or that it’s like a neutral drop. So who would ever pay to have one designed by a huge company that says they could do it).

Now a trans-brake offers = True Stall, the highest potential stall possible. It does this by literally engaging drive and reverse in the transmission, you’re not moving the car and the load is HUGE!!! We can gain stall AND stall up faster by getting closer and closer to the trans-brake drive train load, here are some ways (by $ and easiest to do)………

  1. Pull the E brake
  2. Neutral blip for peak vacuum
  3. Add vacuum pump (25+ inches)
  4. Brake pads with more bite (coefficent)
  5. Hydraulic E brake
  6. Retrofit a bigger brake booster (3G booster offers more pressure and great for a daily driver too)
  7. A smaller master cylinder bore (more pressure but drag only IMO)
  8. Manual brakes (drag only)
  9. Customize a Hydroboost setup (I’m not aware of anyone’s that’s done it but 2500psi of brake pressure is gonna clamp down those pads tight)

Ideally combinations of the above will get the job done, some are ideas that work on other platforms but yet to see on a DSM. Brake mods could be the small push your stall needed to get over the rpm hump and really launch hard.

Part 2 = E85. E85 will add cylinder cooling and extra torque which has been proven to gain stall vs gas. Also the extra un-burnt fuel does wonders in your exhaust housing.

Part 3 = More Low End Torque. This might seem obvious but I still see auto Dsms that want to be non nitrous street cars with huge cams and drag intake manifolds. These 2 performance mods make your auto accelerate slower, this is a fact. Those mods might make more top end power but they sacrifice precious torque your converter craves to blast your car from 0mph to 50mph (roughly 1st gear) in an instant. If you build an 1/8th mile auto car the majority of the non nitrous DSM enthusiasts will be very happy with its performance.

 

I’m swapping from manual to auto, what tips do you have to run high 9s without nitrous?

1st, ignore most of the performance engine parts manual DSM’s purchase to run high 9s. Think 1/8th mile vs 1/4 mile and don’t chase dyno numbers but instead E.T. numbers.

  1. A 62mm turbo has plenty of power to reach this goal, some do it with smaller so don’t bother with 67mm etc monsters.
  2. Our Spoolinator torque converter will stall high enough to launch in the 1.4x range and tightly couples the psi level you’d most likely run without major slippage.
  3. Cams bigger than FP2, 272 or GSC 2 are going to slow your acceleration. If you have 280 cams, degree them for low end torque to get back the bottom and mid range torque curve.
  4. Any intake smaller than a Drag or huge custom sheet metal intake will get the job done. I’ve seen customers sell the big ones for the smaller ones and go faster (acceleration wins again).
  5. A pro launch tune makes a huge difference, a great tune by a manual tuner on an auto has sometimes been an issue so find a proven auto launch tuner.
  6. High launch timing
  7. Brake mods
  8. 2 step
  9. Transmission upgrades to handle the power.
  10. Plenty more but this is already too long.

 

Should I consider running performance transmission fluid?

Yes and no. The secret to fluid life is the temperature it’s constantly run at over time. Run a giant Bar/Plate trans cooler with a fan attached, that turns on at 160 degrees, and you’re clutches are going to live a longer life. Regular ATF+4 can definitely survive in this scenario, but if you hot lap at the track and drive it as a spirited daily car without a cooler fan, consider Red Line fluid as added insurance. Plain and simple, huge cooler with a fan turned on in the 160-180 range will get it done for the majority of Dsm owners (as long as the converter doesn’t slip to much and cause crazy high temps at the traps).

 

What is the most overlooked part in the performance auto transmission?

Easy = transmission pump. Nothing like trusting a 24 year old trans pump to push fluid through your $3000 transmission rebuild. Rebuild the heart of your trans, strong fluid flow is an upgrade and insurance for the next 20 years.